test: add Tier 3 refractor test cases (T3-1, T3-6, T3-7, T3-8)

Adds four Tier 3 (medium-priority) test cases to the existing refractor test
suite.  All tests use SQLite in-memory databases and run without a PostgreSQL
connection.

T3-1 (test_refractor_track_api.py): Two tests verifying that
  GET /api/v2/refractor/tracks?card_type= returns 200 with count=0 for both
  an unrecognised card_type value ('foo') and an empty string, rather than
  a 4xx/5xx.  A full SQLite-backed TestClient is added to the track API test
  module for these cases.

T3-6 (test_refractor_state_api.py): Verifies that
  GET /api/v2/refractor/cards/{card_id} returns last_evaluated_at: null (not
  a crash or missing key) when the RefractorCardState was initialised but
  never evaluated.  Adds the SQLite test infrastructure (models, fixtures,
  helper factories, TestClient) to the state API test module.

T3-7 (test_refractor_evaluator.py): Two tests covering fully_evolved/tier
  mismatch correction.  When the database has fully_evolved=True but
  current_tier=3 (corruption), evaluate_card must re-derive fully_evolved
  from the freshly-computed tier (False for tier 3, True for tier 4).

T3-8 (test_refractor_evaluator.py): Two tests confirming per-team stat
  isolation.  A player with BattingSeasonStats on two different teams must
  have each team's RefractorCardState reflect only that team's stats — not
  a combined total.  Covers both same-season and multi-season scenarios.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/test_formula_engine.py

@@ -204,3 +204,120 @@ def test_tier_t3_boundary():
 def test_tier_accepts_namespace_track():
     """tier_from_value must work with attribute-style track objects (Peewee models)."""
     assert tier_from_value(37, track_ns("batter")) == 1
+
+
+# ---------------------------------------------------------------------------
+# T1-1: Negative singles guard in compute_batter_value
+# ---------------------------------------------------------------------------
+
+
+def test_batter_negative_singles_component():
+    """hits=1, doubles=1, triples=1, hr=0 produces singles=-1.
+
+    What: The formula computes singles = hits - doubles - triples - hr.
+    With hits=1, doubles=1, triples=1, hr=0 the result is singles = -1,
+    which is a physically impossible stat line but valid arithmetic input.
+
+    Why: Document the formula's actual behaviour when given an incoherent stat
+    line so that callers are aware that no clamping or guard exists.  If a
+    guard is added in the future, this test will catch the change in behaviour.
+
+    singles = 1 - 1 - 1 - 0 = -1
+    tb      = (-1)*1 + 1*2 + 1*3 + 0*4 = -1 + 2 + 3 = 4
+    value   = pa + tb*2 = 0 + 4*2 = 8
+    """
+    stats = batter_stats(hits=1, doubles=1, triples=1, hr=0)
+    # singles will be -1; the formula does NOT clamp, so TB = 4 and value = 8.0
+    result = compute_batter_value(stats)
+    assert result == 8.0, (
+        f"Expected 8.0 (negative singles flows through unclamped), got {result}"
+    )
+
+
+def test_batter_negative_singles_is_not_clamped():
+    """A singles value below zero is NOT clamped to zero by the formula.
+
+    What: Confirms that singles < 0 propagates into TB rather than being
+    floored at 0.  If clamping were added, tb would be 0*1 + 1*2 + 1*3 = 5
+    and value would be 10.0, not 8.0.
+
+    Why: Guards future refactors — if someone adds `singles = max(0, ...)`,
+    this assertion will fail immediately, surfacing the behaviour change.
+    """
+    stats = batter_stats(hits=1, doubles=1, triples=1, hr=0)
+    unclamped_value = compute_batter_value(stats)
+    # If singles were clamped to 0: tb = 0+2+3 = 5, value = 10.0
+    clamped_value = 10.0
+    assert unclamped_value != clamped_value, (
+        "Formula appears to clamp negative singles — behaviour has changed"
+    )
+
+
+# ---------------------------------------------------------------------------
+# T1-2: Tier boundary precision with float SP values
+# ---------------------------------------------------------------------------
+
+
+def test_sp_tier_just_below_t1_outs29():
+    """SP with outs=29 produces IP=9.666..., which is below T1 threshold (10) → T0.
+
+    What: 29 outs / 3 = 9.6666... IP + 0 K = 9.6666... value.
+    The SP T1 threshold is 10.0, so this value is strictly below T1.
+
+    Why: Floating-point IP values accumulate slowly for pitchers.  A bug that
+    truncated or rounded IP upward could cause premature tier advancement.
+    Verify that tier_from_value uses a >= comparison (not >) and handles
+    non-integer values correctly.
+    """
+    stats = pitcher_stats(outs=29, strikeouts=0)
+    value = compute_sp_value(stats)
+    assert value == pytest.approx(29 / 3)  # 9.6666...
+    assert value < 10.0  # strictly below T1
+    assert tier_from_value(value, track_dict("sp")) == 0
+
+
+def test_sp_tier_exactly_t1_outs30():
+    """SP with outs=30 produces IP=10.0, exactly at T1 threshold → T1.
+
+    What: 30 outs / 3 = 10.0 IP + 0 K = 10.0 value.
+    The SP T1 threshold is 10.0, so value == t1 satisfies the >= condition.
+
+    Why: Off-by-one or strictly-greater-than comparisons would classify
+    this as T0 instead of T1.  The boundary value must correctly promote
+    to the matching tier.
+    """
+    stats = pitcher_stats(outs=30, strikeouts=0)
+    value = compute_sp_value(stats)
+    assert value == 10.0
+    assert tier_from_value(value, track_dict("sp")) == 1
+
+
+def test_sp_float_value_at_exact_t2_boundary():
+    """SP value exactly at T2 threshold (40.0) → T2.
+
+    What: outs=120 -> IP=40.0, strikeouts=0 -> value=40.0.
+    T2 threshold for SP is 40.  The >= comparison must promote to T2.
+
+    Why: Validates that all four tier thresholds use inclusive lower-bound
+    comparisons for float values, not just T1.
+    """
+    stats = pitcher_stats(outs=120, strikeouts=0)
+    value = compute_sp_value(stats)
+    assert value == 40.0
+    assert tier_from_value(value, track_dict("sp")) == 2
+
+
+def test_sp_float_value_just_below_t2():
+    """SP value just below T2 (39.999...) stays at T1.
+
+    What: outs=119 -> IP=39.6666..., strikeouts=0 -> value=39.666...
+    This is strictly less than T2=40, so tier should be 1 (already past T1=10).
+
+    Why: Confirms that sub-threshold float values are not prematurely promoted
+    due to floating-point comparison imprecision.
+    """
+    stats = pitcher_stats(outs=119, strikeouts=0)
+    value = compute_sp_value(stats)
+    assert value == pytest.approx(119 / 3)  # 39.666...
+    assert value < 40.0
+    assert tier_from_value(value, track_dict("sp")) == 1

tests/test_postgame_refractor.py

@@ -665,3 +665,136 @@ def test_auth_required_evaluate_game(client):
 
     resp = client.post(f"/api/v2/refractor/evaluate-game/{game.id}")
     assert resp.status_code == 401
+
+
+# ---------------------------------------------------------------------------
+# T1-3: evaluate-game with non-existent game_id
+# ---------------------------------------------------------------------------
+
+
+def test_evaluate_game_nonexistent_game_id(client):
+    """POST /refractor/evaluate-game/99999 with a game_id that does not exist.
+
+    What: There is no StratGame row with id=99999.  The endpoint queries
+    StratPlay for plays in that game, finds zero rows, builds an empty
+    pairs set, and returns without evaluating anyone.
+
+    Why: Documents the confirmed behaviour: 200 with {"evaluated": 0,
+    "tier_ups": []}.  The endpoint does not treat a missing game as an
+    error because StratPlay.select().where(game_id=N) returning 0 rows is
+    a valid (if unusual) outcome — there are simply no players to evaluate.
+
+    If the implementation is ever changed to return 404 for missing games,
+    this test will fail and alert the developer to update the contract.
+    """
+    resp = client.post("/api/v2/refractor/evaluate-game/99999", headers=AUTH_HEADER)
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["evaluated"] == 0
+    assert data["tier_ups"] == []
+
+
+# ---------------------------------------------------------------------------
+# T2-3: evaluate-game with zero plays
+# ---------------------------------------------------------------------------
+
+
+def test_evaluate_game_zero_plays(client):
+    """evaluate-game on a game with no StratPlay rows returns empty results.
+
+    What: Create a StratGame but insert zero StratPlay rows for it.  POST
+    to evaluate-game for that game_id.
+
+    Why: The endpoint builds its player list from StratPlay rows.  A game
+    with no plays has no players to evaluate.  Verify the endpoint does not
+    crash and returns the expected empty-batch shape rather than raising a
+    KeyError or returning an unexpected structure.
+    """
+    team_a = _make_team("ZP1", gmid=20101)
+    team_b = _make_team("ZP2", gmid=20102)
+    game = _make_game(team_a, team_b)
+    # Intentionally no plays created
+
+    resp = client.post(
+        f"/api/v2/refractor/evaluate-game/{game.id}", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["evaluated"] == 0
+    assert data["tier_ups"] == []
+
+
+# ---------------------------------------------------------------------------
+# T2-9: Per-player error isolation in evaluate_game
+# ---------------------------------------------------------------------------
+
+
+def test_evaluate_game_error_isolation(client, monkeypatch):
+    """An exception raised for one player does not abort the rest of the batch.
+
+    What: Create two batters in the same game.  Both have RefractorCardState
+    rows.  Patch evaluate_card in the refractor router to raise RuntimeError
+    on the first call and succeed on the second.  Verify the endpoint returns
+    200, evaluated==1 (not 0 or 2), and no tier_ups from the failing player.
+
+    Why: The evaluate-game loop catches per-player exceptions and logs them.
+    If the isolation breaks, a single bad card would silently drop all
+    evaluations for the rest of the game.  The 'evaluated' count is the
+    observable signal that error isolation is functioning.
+
+    Implementation note: we patch the evaluate_card function inside the
+    router module directly so that the test is independent of how the router
+    imports it.  We use a counter to let the first call fail and the second
+    succeed.
+    """
+    from app.services import refractor_evaluator
+
+    team_a = _make_team("EI1", gmid=20111)
+    team_b = _make_team("EI2", gmid=20112)
+
+    batter_fail = _make_player("WP13 Fail Batter", pos="1B")
+    batter_ok = _make_player("WP13 Ok Batter", pos="1B")
+    pitcher = _make_player("WP13 EI Pitcher", pos="SP")
+
+    game = _make_game(team_a, team_b)
+
+    # Both batters need season stats and a track/state so they are not
+    # skipped by the "no state" guard before evaluate_card is called.
+    track = _make_track(name="EI Batter Track")
+    _make_state(batter_fail, team_a, track)
+    _make_state(batter_ok, team_a, track)
+
+    _make_play(game, 1, batter_fail, team_a, pitcher, team_b, pa=1, ab=1, outs=1)
+    _make_play(game, 2, batter_ok, team_a, pitcher, team_b, pa=1, ab=1, outs=1)
+
+    # The real evaluate_card for batter_ok so we know what it returns
+    real_evaluate = refractor_evaluator.evaluate_card
+
+    call_count = {"n": 0}
+    fail_player_id = batter_fail.player_id
+
+    def patched_evaluate(player_id, team_id, **kwargs):
+        call_count["n"] += 1
+        if player_id == fail_player_id:
+            raise RuntimeError("simulated per-player error")
+        return real_evaluate(player_id, team_id, **kwargs)
+
+    # The router does `from ..services.refractor_evaluator import evaluate_card`
+    # inside the async function body, so the local import re-resolves on each
+    # call.  Patching the function on its source module ensures the local `from`
+    # import picks up our patched version when the route handler executes.
+    monkeypatch.setattr(
+        "app.services.refractor_evaluator.evaluate_card", patched_evaluate
+    )
+
+    resp = client.post(
+        f"/api/v2/refractor/evaluate-game/{game.id}", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+
+    # One player succeeded; one was caught by the exception handler
+    assert data["evaluated"] == 1
+    # The failing player must not appear in tier_ups
+    failing_ids = [tu["player_id"] for tu in data["tier_ups"]]
+    assert fail_player_id not in failing_ids

tests/test_refractor_evaluator.py

@@ -325,6 +325,59 @@ class TestCareerTotals:
         assert result["current_value"] == 50.0
 
 
+class TestFullyEvolvedPersistence:
+    """T2-1: fully_evolved=True is preserved even when stats drop or are absent."""
+
+    def test_fully_evolved_persists_when_stats_zeroed(self, batter_track):
+        """Card at T4/fully_evolved=True stays fully_evolved after stats are removed.
+
+        What: Set up a RefractorCardState at tier=4 with fully_evolved=True.
+        Then call evaluate_card with no season stats rows (zero career totals).
+        The evaluator computes value=0 -> new_tier=0, but current_tier must
+        stay at 4 (no regression) and fully_evolved must remain True.
+
+        Why: fully_evolved is a permanent achievement flag — it must not be
+        revoked if a team's stats are rolled back, corrected, or simply not
+        yet imported.  The no-regression rule (max(current, new)) prevents
+        tier demotion; this test confirms that fully_evolved follows the same
+        protection.
+        """
+        # Seed state at T4 fully_evolved
+        _make_state(1, 1, batter_track, current_tier=4, current_value=900.0)
+        # No stats rows — career totals will be all zeros
+        # (no _make_stats call)
+
+        result = _eval(1, 1)
+
+        # The no-regression rule keeps tier at 4
+        assert result["current_tier"] == 4, (
+            f"Expected tier=4 (no regression), got {result['current_tier']}"
+        )
+        # fully_evolved must still be True since tier >= 4
+        assert result["fully_evolved"] is True, (
+            "fully_evolved was reset to False after re-evaluation with zero stats"
+        )
+
+    def test_fully_evolved_persists_with_partial_stats(self, batter_track):
+        """Card at T4 stays fully_evolved even with stats below T1.
+
+        What: Same setup as above but with a season stats row giving value=30
+        (below T1=37).  The computed tier would be 0, but current_tier must
+        not regress from 4.
+
+        Why: Validates that no-regression applies regardless of whether stats
+        are zero or merely insufficient for the achieved tier.
+        """
+        _make_state(1, 1, batter_track, current_tier=4, current_value=900.0)
+        # pa=30 -> value=30, which is below T1=37 -> computed tier=0
+        _make_stats(1, 1, 1, pa=30)
+
+        result = _eval(1, 1)
+
+        assert result["current_tier"] == 4
+        assert result["fully_evolved"] is True
+
+
 class TestMissingState:
     """ValueError when no card state exists for (player_id, team_id)."""
 
@@ -359,3 +412,212 @@ class TestReturnShape:
         assert isinstance(ts, str) and len(ts) > 0
         # Must be parseable as a datetime
         datetime.fromisoformat(ts)
+
+
+class TestFullyEvolvedFlagCorrection:
+    """T3-7: fully_evolved/tier mismatch is corrected by evaluate_card.
+
+    A database corruption where fully_evolved=True but current_tier < 4 can
+    occur if the flag was set incorrectly by a migration or external script.
+    evaluate_card must re-derive fully_evolved from the freshly-computed tier
+    (after the no-regression max() is applied), not trust the stored flag.
+    """
+
+    def test_fully_evolved_flag_corrected_when_tier_below_4(self, batter_track):
+        """fully_evolved=True with current_tier=3 is corrected to False after evaluation.
+
+        What: Manually set database state to fully_evolved=True, current_tier=3
+        (a corruption scenario — tier 3 cannot be "fully evolved" since T4 is
+        the maximum tier).  Provide stats that compute to a value in the T3
+        range (value=500, which is >= T3=448 but < T4=896).
+
+        After evaluate_card:
+          - computed value = 500 → new_tier = 3
+          - no-regression: max(current_tier=3, new_tier=3) = 3  → tier stays 3
+          - fully_evolved = (3 >= 4) = False  → flag is corrected
+
+        Why: The evaluator always recomputes fully_evolved from the final
+        current_tier rather than preserving the stored flag.  This ensures
+        that a corrupted fully_evolved=True at tier<4 is silently repaired
+        on the next evaluation without requiring a separate migration.
+        """
+        # Inject corruption: fully_evolved=True but tier=3
+        state = CardStateStub.create(
+            player_id=1,
+            team_id=1,
+            track=batter_track,
+            current_tier=3,
+            current_value=500.0,
+            fully_evolved=True,  # intentionally wrong
+            last_evaluated_at=None,
+        )
+        # Stats that compute to value=500: pa=500, no hits → value=500+0=500
+        # T3 threshold=448, T4 threshold=896 → tier=3, NOT 4
+        _make_stats(1, 1, 1, pa=500)
+
+        result = _eval(1, 1)
+
+        assert result["current_tier"] == 3, (
+            f"Expected tier=3 after evaluation with value=500, got {result['current_tier']}"
+        )
+        assert result["fully_evolved"] is False, (
+            "fully_evolved should have been corrected to False for tier=3, "
+            f"got {result['fully_evolved']}"
+        )
+
+        # Confirm the database row was updated (not just the return dict)
+        state_reloaded = CardStateStub.get_by_id(state.id)
+        assert state_reloaded.fully_evolved is False, (
+            "fully_evolved was not persisted as False after correction"
+        )
+
+    def test_fully_evolved_flag_preserved_when_tier_reaches_4(self, batter_track):
+        """fully_evolved=True with current_tier=3 stays True when new stats push to T4.
+
+        What: Same corruption setup as above (fully_evolved=True, tier=3),
+        but now provide stats with value=900 (>= T4=896).
+
+        After evaluate_card:
+          - computed value = 900 → new_tier = 4
+          - no-regression: max(current_tier=3, new_tier=4) = 4  → advances to 4
+          - fully_evolved = (4 >= 4) = True  → flag stays True (correctly)
+
+        Why: Confirms the evaluator correctly sets fully_evolved=True when
+        the re-computed tier legitimately reaches T4 regardless of whether
+        the stored flag was already True before evaluation.
+        """
+        CardStateStub.create(
+            player_id=1,
+            team_id=1,
+            track=batter_track,
+            current_tier=3,
+            current_value=500.0,
+            fully_evolved=True,  # stored flag (will be re-derived)
+            last_evaluated_at=None,
+        )
+        # pa=900 → value=900 >= T4=896 → new_tier=4
+        _make_stats(1, 1, 1, pa=900)
+
+        result = _eval(1, 1)
+
+        assert result["current_tier"] == 4, (
+            f"Expected tier=4 for value=900, got {result['current_tier']}"
+        )
+        assert result["fully_evolved"] is True, (
+            f"Expected fully_evolved=True for tier=4, got {result['fully_evolved']}"
+        )
+
+
+class TestMultiTeamStatIsolation:
+    """T3-8: A player's refractor value is isolated to a specific team's stats.
+
+    The evaluator queries BattingSeasonStats WHERE player_id=? AND team_id=?.
+    When a player has stats on two different teams in the same season, each
+    team's RefractorCardState must reflect only that team's stats — not a
+    combined total.
+    """
+
+    def test_multi_team_same_season_stats_isolated(self, batter_track):
+        """Each team's refractor value reflects only that team's stats, not combined.
+
+        What: Create one player with BattingSeasonStats on team_id=1 (pa=80)
+        and team_id=2 (pa=120) in the same season.  Create a RefractorCardState
+        for each team.  Evaluate each team's card separately and verify:
+          - Team 1 state: value = 80 → tier = T1 (80 >= T1=37, < T2=149)
+          - Team 2 state: value = 120 → tier = T1 (120 >= T1=37, < T2=149)
+          - Neither value equals the combined total (80+120=200 → would be T2)
+
+        Why: Confirms the `WHERE player_id=? AND team_id=?` filter in the
+        evaluator is correctly applied.  Without proper team isolation, the
+        combined total of 200 would cross the T2 threshold (149) and both
+        states would be incorrectly assigned to T2.  This is a critical
+        correctness requirement: a player traded between teams should have
+        separate refractor progressions for their time with each franchise.
+        """
+        # Stats on team 1: pa=80 → value=80 (T1: 37<=80<149)
+        _make_stats(player_id=1, team_id=1, season=11, pa=80)
+        # Stats on team 2: pa=120 → value=120 (T1: 37<=120<149)
+        _make_stats(player_id=1, team_id=2, season=11, pa=120)
+
+        # combined pa would be 200 → value=200 → T2 (149<=200<448)
+        # Each team must see only its own stats, not 200
+
+        _make_state(player_id=1, team_id=1, track=batter_track)
+        _make_state(player_id=1, team_id=2, track=batter_track)
+
+        result_team1 = _eval(player_id=1, team_id=1)
+        result_team2 = _eval(player_id=1, team_id=2)
+
+        # Team 1: only pa=80 counted → value=80 → T1
+        assert result_team1["current_value"] == 80.0, (
+            f"Team 1 value should be 80.0 (its own stats only), "
+            f"got {result_team1['current_value']}"
+        )
+        assert result_team1["current_tier"] == 1, (
+            f"Team 1 tier should be T1 for value=80, got {result_team1['current_tier']}"
+        )
+
+        # Team 2: only pa=120 counted → value=120 → T1
+        assert result_team2["current_value"] == 120.0, (
+            f"Team 2 value should be 120.0 (its own stats only), "
+            f"got {result_team2['current_value']}"
+        )
+        assert result_team2["current_tier"] == 1, (
+            f"Team 2 tier should be T1 for value=120, got {result_team2['current_tier']}"
+        )
+
+        # Sanity: neither team crossed T2 (which would happen if stats were combined)
+        assert (
+            result_team1["current_tier"] != 2 and result_team2["current_tier"] != 2
+        ), (
+            "At least one team was incorrectly assigned T2 — stats may have been combined"
+        )
+
+    def test_multi_team_different_seasons_isolated(self, batter_track):
+        """Stats for the same player across multiple seasons remain per-team isolated.
+
+        What: Same player with two seasons of stats for each of two teams:
+          - team_id=1: season 10 pa=90, season 11 pa=70 → combined=160
+          - team_id=2: season 10 pa=100, season 11 pa=80 → combined=180
+
+        After evaluation:
+          - Team 1: value=160 → T2 (149<=160<448)
+          - Team 2: value=180 → T2 (149<=180<448)
+
+        The test confirms that cross-team season aggregation does not bleed
+        stats from team 2 into team 1's calculation or vice versa.
+
+        Why: Multi-season aggregation and multi-team isolation must work
+        together.  A bug that incorrectly sums all player stats regardless
+        of team would produce combined values of 340 → T2, which coincidentally
+        passes, but the per-team values and tiers would be wrong.
+        This test uses values where cross-contamination would produce a
+        materially different value (340 vs 160/180), catching that class of bug.
+        """
+        # Team 1 stats: total pa=160 → value=160 → T2
+        _make_stats(player_id=1, team_id=1, season=10, pa=90)
+        _make_stats(player_id=1, team_id=1, season=11, pa=70)
+
+        # Team 2 stats: total pa=180 → value=180 → T2
+        _make_stats(player_id=1, team_id=2, season=10, pa=100)
+        _make_stats(player_id=1, team_id=2, season=11, pa=80)
+
+        _make_state(player_id=1, team_id=1, track=batter_track)
+        _make_state(player_id=1, team_id=2, track=batter_track)
+
+        result_team1 = _eval(player_id=1, team_id=1)
+        result_team2 = _eval(player_id=1, team_id=2)
+
+        assert result_team1["current_value"] == 160.0, (
+            f"Team 1 multi-season value should be 160.0, got {result_team1['current_value']}"
+        )
+        assert result_team1["current_tier"] == 2, (
+            f"Team 1 tier should be T2 for value=160, got {result_team1['current_tier']}"
+        )
+
+        assert result_team2["current_value"] == 180.0, (
+            f"Team 2 multi-season value should be 180.0, got {result_team2['current_value']}"
+        )
+        assert result_team2["current_tier"] == 2, (
+            f"Team 2 tier should be T2 for value=180, got {result_team2['current_tier']}"
+        )

tests/test_refractor_init.py

@@ -158,6 +158,50 @@ class TestDetermineCardType:
 # ---------------------------------------------------------------------------
 
 
+class TestDetermineCardTypeEdgeCases:
+    """T2-2: Parametrized edge cases for _determine_card_type.
+
+    Covers all the boundary inputs identified in the PO review:
+    DH, C, 2B (batters), empty string, None, and the compound 'SP/RP'
+    which contains both 'SP' and 'RP' substrings.
+
+    The function checks 'SP' before 'RP'/'CP', so 'SP/RP' resolves to 'sp'.
+    """
+
+    @pytest.mark.parametrize(
+        "pos_1, expected",
+        [
+            # Plain batter positions
+            ("DH", "batter"),
+            ("C", "batter"),
+            ("2B", "batter"),
+            # Empty / None — fall through to batter default
+            ("", "batter"),
+            (None, "batter"),
+            # Compound string containing 'SP' first — must resolve to 'sp'
+            # because _determine_card_type checks "SP" in pos.upper() before RP/CP
+            ("SP/RP", "sp"),
+        ],
+    )
+    def test_position_mapping(self, pos_1, expected):
+        """_determine_card_type maps each pos_1 value to the expected card_type.
+
+        What: Directly exercises _determine_card_type with the given pos_1 string.
+        None is handled by the `(player.pos_1 or "").upper()` guard in the
+        implementation, so it falls through to 'batter'.
+
+        Why: The card_type string is the key used to look up a RefractorTrack.
+        An incorrect mapping silently assigns the wrong thresholds to a player's
+        entire refractor journey.  Parametrized so each edge case is a
+        distinct, independently reported test failure.
+        """
+        player = _FakePlayer(pos_1)
+        assert _determine_card_type(player) == expected, (
+            f"pos_1={pos_1!r}: expected {expected!r}, "
+            f"got {_determine_card_type(player)!r}"
+        )
+
+
 class TestInitializeCardEvolution:
     """Integration tests for initialize_card_refractor against in-memory SQLite.
 

tests/test_refractor_seed.py

@@ -124,6 +124,89 @@ def test_seed_idempotent():
     assert RefractorTrack.select().count() == 3
 
 
+# ---------------------------------------------------------------------------
+# T1-4: Seed threshold ordering invariant (t1 < t2 < t3 < t4 + all positive)
+# ---------------------------------------------------------------------------
+
+
+def test_seed_all_thresholds_strictly_ascending_after_seed():
+    """After seeding, every track satisfies t1 < t2 < t3 < t4.
+
+    What: Call seed_refractor_tracks(), then assert the full ordering chain
+    t1 < t2 < t3 < t4 for every row in the database.  Also assert that all
+    four thresholds are strictly positive (> 0).
+
+    Why: The refractor tier engine uses these thresholds as exclusive partition
+    points.  If any threshold is out-of-order or zero the tier assignment
+    becomes incorrect or undefined.  This test is the authoritative invariant
+    guard; if a JSON edit accidentally violates the ordering this test fails
+    loudly before any cards are affected.
+
+    Separate from test_seed_thresholds_ascending which was written earlier —
+    this test combines ordering + positivity into a single explicit assertion
+    block and uses more descriptive messages to aid debugging.
+    """
+    seed_refractor_tracks()
+    for track in RefractorTrack.select():
+        assert track.t1_threshold > 0, (
+            f"{track.name}: t1_threshold={track.t1_threshold} is not positive"
+        )
+        assert track.t2_threshold > 0, (
+            f"{track.name}: t2_threshold={track.t2_threshold} is not positive"
+        )
+        assert track.t3_threshold > 0, (
+            f"{track.name}: t3_threshold={track.t3_threshold} is not positive"
+        )
+        assert track.t4_threshold > 0, (
+            f"{track.name}: t4_threshold={track.t4_threshold} is not positive"
+        )
+        assert (
+            track.t1_threshold
+            < track.t2_threshold
+            < track.t3_threshold
+            < track.t4_threshold
+        ), (
+            f"{track.name}: thresholds are not strictly ascending: "
+            f"t1={track.t1_threshold}, t2={track.t2_threshold}, "
+            f"t3={track.t3_threshold}, t4={track.t4_threshold}"
+        )
+
+
+# ---------------------------------------------------------------------------
+# T2-10: Duplicate card_type tracks guard
+# ---------------------------------------------------------------------------
+
+
+def test_seed_each_card_type_has_exactly_one_track():
+    """Each card_type must appear exactly once across all RefractorTrack rows.
+
+    What: After seeding, group the rows by card_type and assert that every
+    card_type has a count of exactly 1.
+
+    Why: RefractorTrack rows are looked up by card_type (e.g.
+    RefractorTrack.get(card_type='batter')).  If a card_type appears more
+    than once, Peewee's .get() raises MultipleObjectsReturned, crashing
+    every pack opening and card evaluation for that type.  This test acts as
+    a uniqueness contract so that seed bugs or accidental DB drift surface
+    immediately.
+    """
+    seed_refractor_tracks()
+    from peewee import fn as peewee_fn
+
+    # Group by card_type and count occurrences
+    query = (
+        RefractorTrack.select(
+            RefractorTrack.card_type, peewee_fn.COUNT(RefractorTrack.id).alias("cnt")
+        )
+        .group_by(RefractorTrack.card_type)
+        .tuples()
+    )
+    for card_type, count in query:
+        assert count == 1, (
+            f"card_type={card_type!r} has {count} tracks; expected exactly 1"
+        )
+
+
 def test_seed_updates_on_rerun(json_tracks):
     """A second seed call must restore any manually changed threshold to the JSON value.
 

tests/test_refractor_state_api.py

@@ -34,12 +34,47 @@ Test matrix
   test_get_card_404_no_state          -- card with no RefractorCardState returns 404
   test_duplicate_cards_share_state    -- two cards same player+team return the same state row
   test_auth_required                  -- missing token returns 401 on both endpoints
+
+Tier 3 tests (T3-6) use a SQLite-backed TestClient and run without a PostgreSQL
+connection.  They test GET /api/v2/refractor/cards/{card_id} when the state row
+has last_evaluated_at=None (card initialised but never evaluated).
+  test_get_card_state_last_evaluated_at_null -- last_evaluated_at: null in response
 """
 
 import os
 
+os.environ.setdefault("API_TOKEN", "test-token")
+
 import pytest
+from fastapi import FastAPI, Request
 from fastapi.testclient import TestClient
+from peewee import SqliteDatabase
+
+from app.db_engine import (
+    BattingSeasonStats,
+    Card,
+    Cardset,
+    Decision,
+    Event,
+    MlbPlayer,
+    Pack,
+    PackType,
+    PitchingSeasonStats,
+    Player,
+    ProcessedGame,
+    Rarity,
+    RefractorCardState,
+    RefractorCosmetic,
+    RefractorTierBoost,
+    RefractorTrack,
+    Roster,
+    RosterSlot,
+    ScoutClaim,
+    ScoutOpportunity,
+    StratGame,
+    StratPlay,
+    Team,
+)
 
 POSTGRES_HOST = os.environ.get("POSTGRES_HOST")
 _skip_no_pg = pytest.mark.skipif(
@@ -607,3 +642,317 @@ def test_auth_required(client, seeded_data):
 
     resp_card = client.get(f"/api/v2/refractor/cards/{card_id}")
     assert resp_card.status_code == 401
+
+
+# ===========================================================================
+# SQLite-backed tests for T2-4, T2-5, T2-6, T3-6
+#
+# These tests use the same shared-memory SQLite pattern as test_postgame_refractor
+# so they run without a PostgreSQL connection.  They test the
+# GET /api/v2/teams/{team_id}/refractors, POST /refractor/cards/{card_id}/evaluate,
+# and GET /api/v2/refractor/cards/{card_id} endpoints in isolation.
+# ===========================================================================
+
+_state_api_db = SqliteDatabase(
+    "file:stateapitest?mode=memory&cache=shared",
+    uri=True,
+    pragmas={"foreign_keys": 1},
+)
+
+_STATE_API_MODELS = [
+    Rarity,
+    Event,
+    Cardset,
+    MlbPlayer,
+    Player,
+    Team,
+    PackType,
+    Pack,
+    Card,
+    Roster,
+    RosterSlot,
+    StratGame,
+    StratPlay,
+    Decision,
+    ScoutOpportunity,
+    ScoutClaim,
+    BattingSeasonStats,
+    PitchingSeasonStats,
+    ProcessedGame,
+    RefractorTrack,
+    RefractorCardState,
+    RefractorTierBoost,
+    RefractorCosmetic,
+]
+
+
+@pytest.fixture(autouse=False)
+def setup_state_api_db():
+    """Bind state-api test models to shared-memory SQLite and create tables.
+
+    Not autouse — only the SQLite-backed tests in this section depend on it.
+    """
+    _state_api_db.bind(_STATE_API_MODELS)
+    _state_api_db.connect(reuse_if_open=True)
+    _state_api_db.create_tables(_STATE_API_MODELS)
+    yield _state_api_db
+    _state_api_db.drop_tables(list(reversed(_STATE_API_MODELS)), safe=True)
+
+
+def _build_state_api_app() -> FastAPI:
+    """Minimal FastAPI app with teams + refractor routers for SQLite tests."""
+    from app.routers_v2.teams import router as teams_router
+    from app.routers_v2.refractor import router as refractor_router
+
+    app = FastAPI()
+
+    @app.middleware("http")
+    async def db_middleware(request: Request, call_next):
+        _state_api_db.connect(reuse_if_open=True)
+        return await call_next(request)
+
+    app.include_router(teams_router)
+    app.include_router(refractor_router)
+    return app
+
+
+@pytest.fixture
+def state_api_client(setup_state_api_db):
+    """FastAPI TestClient for the SQLite-backed state API tests."""
+    with TestClient(_build_state_api_app()) as c:
+        yield c
+
+
+# ---------------------------------------------------------------------------
+# Helper factories for SQLite-backed tests
+# ---------------------------------------------------------------------------
+
+
+def _sa_make_rarity():
+    r, _ = Rarity.get_or_create(
+        value=50, name="SA_Common", defaults={"color": "#aabbcc"}
+    )
+    return r
+
+
+def _sa_make_cardset():
+    cs, _ = Cardset.get_or_create(
+        name="SA Test Set",
+        defaults={"description": "state api test", "total_cards": 10},
+    )
+    return cs
+
+
+def _sa_make_team(abbrev: str, gmid: int) -> Team:
+    return Team.create(
+        abbrev=abbrev,
+        sname=abbrev,
+        lname=f"Team {abbrev}",
+        gmid=gmid,
+        gmname=f"gm_{abbrev.lower()}",
+        gsheet="https://docs.google.com/sa_test",
+        wallet=500,
+        team_value=1000,
+        collection_value=1000,
+        season=11,
+        is_ai=False,
+    )
+
+
+def _sa_make_player(name: str, pos: str = "1B") -> Player:
+    return Player.create(
+        p_name=name,
+        rarity=_sa_make_rarity(),
+        cardset=_sa_make_cardset(),
+        set_num=1,
+        pos_1=pos,
+        image="https://example.com/sa.png",
+        mlbclub="TST",
+        franchise="TST",
+        description=f"sa test: {name}",
+    )
+
+
+def _sa_make_track(card_type: str = "batter") -> RefractorTrack:
+    track, _ = RefractorTrack.get_or_create(
+        name=f"SA {card_type} Track",
+        defaults=dict(
+            card_type=card_type,
+            formula="pa + tb * 2",
+            t1_threshold=37,
+            t2_threshold=149,
+            t3_threshold=448,
+            t4_threshold=896,
+        ),
+    )
+    return track
+
+
+def _sa_make_pack(team: Team) -> Pack:
+    pt, _ = PackType.get_or_create(
+        name="SA PackType",
+        defaults={"cost": 100, "card_count": 5, "description": "sa test pack type"},
+    )
+    return Pack.create(team=team, pack_type=pt)
+
+
+def _sa_make_card(player: Player, team: Team) -> Card:
+    pack = _sa_make_pack(team)
+    return Card.create(player=player, team=team, pack=pack, value=0)
+
+
+def _sa_make_state(player, team, track, current_tier=0, current_value=0.0):
+    return RefractorCardState.create(
+        player=player,
+        team=team,
+        track=track,
+        current_tier=current_tier,
+        current_value=current_value,
+        fully_evolved=False,
+        last_evaluated_at=None,
+    )
+
+
+# ---------------------------------------------------------------------------
+# T2-4: GET /teams/{valid_team_id}/refractors — team exists, zero states
+# ---------------------------------------------------------------------------
+
+
+def test_team_refractors_zero_states(setup_state_api_db, state_api_client):
+    """GET /teams/{id}/refractors for a team with no RefractorCardState rows.
+
+    What: Create a Team with no associated RefractorCardState rows.
+    Call the endpoint and verify the response is {"count": 0, "items": []}.
+
+    Why: The endpoint uses a JOIN from RefractorCardState to RefractorTrack
+    filtered by team_id.  If the WHERE produces no rows, the correct response
+    is an empty list with count=0, not a 404 or 500.  This is the base-case
+    for a newly-created team that hasn't opened any packs yet.
+    """
+    team = _sa_make_team("SA4", gmid=30041)
+
+    resp = state_api_client.get(
+        f"/api/v2/teams/{team.id}/refractors", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["count"] == 0
+    assert data["items"] == []
+
+
+# ---------------------------------------------------------------------------
+# T2-5: GET /teams/99999/refractors — non-existent team
+# ---------------------------------------------------------------------------
+
+
+def test_team_refractors_nonexistent_team(setup_state_api_db, state_api_client):
+    """GET /teams/99999/refractors where team_id 99999 does not exist.
+
+    What: Call the endpoint with a team_id that has no Team row and no
+    RefractorCardState rows.
+
+    Why: Documents the confirmed behaviour: 200 with {"count": 0, "items": []}.
+    The endpoint queries RefractorCardState WHERE team_id=99999.  Because no
+    state rows reference that team, the result is an empty list.  The endpoint
+    does NOT validate that the Team row itself exists, so it does not return 404.
+
+    If the implementation is ever changed to validate team existence and return
+    404 for missing teams, this test will fail and surface the contract change.
+    """
+    resp = state_api_client.get("/api/v2/teams/99999/refractors", headers=AUTH_HEADER)
+    assert resp.status_code == 200
+    data = resp.json()
+    # No state rows reference team 99999 — empty list with count=0
+    assert data["count"] == 0
+    assert data["items"] == []
+
+
+# ---------------------------------------------------------------------------
+# T2-6: POST /refractor/cards/{card_id}/evaluate — zero season stats → T0
+# ---------------------------------------------------------------------------
+
+
+def test_evaluate_card_zero_stats_stays_t0(setup_state_api_db, state_api_client):
+    """POST /cards/{card_id}/evaluate for a card with no season stats stays at T0.
+
+    What: Create a Player, Team, Card, and RefractorCardState.  Do NOT create
+    any BattingSeasonStats rows for this player+team.  Call the evaluate
+    endpoint.  The response must show current_tier=0 and current_value=0.0.
+
+    Why: A player who has never appeared in a game has zero career stats.
+    The evaluator sums all stats rows (none) -> all-zero totals ->
+    compute_batter_value(zeros) = 0.0 -> tier_from_value(0.0) = T0.
+    Verifies the happy-path zero-stats case returns a valid response rather
+    than crashing on an empty aggregation.
+    """
+    team = _sa_make_team("SA6", gmid=30061)
+    player = _sa_make_player("SA6 Batter", pos="1B")
+    track = _sa_make_track("batter")
+    card = _sa_make_card(player, team)
+    _sa_make_state(player, team, track, current_tier=0, current_value=0.0)
+
+    # No BattingSeasonStats rows — intentionally empty
+
+    resp = state_api_client.post(
+        f"/api/v2/refractor/cards/{card.id}/evaluate", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["current_tier"] == 0
+    assert data["current_value"] == 0.0
+
+
+# ---------------------------------------------------------------------------
+# T3-6: GET /refractor/cards/{card_id} — last_evaluated_at is None
+# ---------------------------------------------------------------------------
+
+
+def test_get_card_state_last_evaluated_at_null(setup_state_api_db, state_api_client):
+    """GET /refractor/cards/{card_id} returns last_evaluated_at: null for un-evaluated card.
+
+    What: Create a Player, Team, Card, and RefractorCardState where
+    last_evaluated_at is explicitly None (the state was initialised via a
+    pack-open hook but has never been through the evaluator).  Call
+    GET /api/v2/refractor/cards/{card_id} and verify:
+      - The response status is 200 (not a 500 crash from calling .isoformat() on None).
+      - The response body contains the key 'last_evaluated_at'.
+      - The value of 'last_evaluated_at' is JSON null (Python None after parsing).
+
+    Why: The _build_card_state_response helper serialises last_evaluated_at
+    with `state.last_evaluated_at.isoformat() if state.last_evaluated_at else None`.
+    This test confirms that the None branch is exercised and the field is always
+    present in the response envelope.  Callers must be able to distinguish
+    "never evaluated" (null) from a real ISO-8601 timestamp, and the API must
+    not crash on a newly-created card that has not yet been evaluated.
+    """
+    team = _sa_make_team("SA_T36", gmid=30360)
+    player = _sa_make_player("T36 Batter", pos="1B")
+    track = _sa_make_track("batter")
+    card = _sa_make_card(player, team)
+
+    # Create state with last_evaluated_at=None — simulates a freshly initialised
+    # card that has not yet been through the evaluator
+    RefractorCardState.create(
+        player=player,
+        team=team,
+        track=track,
+        current_tier=0,
+        current_value=0.0,
+        fully_evolved=False,
+        last_evaluated_at=None,
+    )
+
+    resp = state_api_client.get(
+        f"/api/v2/refractor/cards/{card.id}", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200, f"Expected 200, got {resp.status_code}: {resp.text}"
+    data = resp.json()
+
+    # 'last_evaluated_at' must be present as a key even when the value is null
+    assert "last_evaluated_at" in data, (
+        "Response is missing the 'last_evaluated_at' key"
+    )
+    assert data["last_evaluated_at"] is None, (
+        f"Expected last_evaluated_at=null for un-evaluated card, "
+        f"got {data['last_evaluated_at']!r}"
+    )

tests/test_refractor_track_api.py

@@ -11,12 +11,47 @@ Tests auto-skip when POSTGRES_HOST is not set.
 Test data is inserted via psycopg2 before the test module runs and deleted
 afterwards so the tests are repeatable.  ON CONFLICT keeps the table clean
 even if a previous run did not complete teardown.
+
+Tier 3 tests (T3-1) in this file use a SQLite-backed TestClient so they run
+without a PostgreSQL connection.  They test the card_type filter edge cases:
+an unrecognised card_type string and an empty string should both return an
+empty list (200 with count=0) rather than an error.
 """
 
 import os
 
 import pytest
+from fastapi import FastAPI, Request
 from fastapi.testclient import TestClient
+from peewee import SqliteDatabase
+
+os.environ.setdefault("API_TOKEN", "test-token")
+
+from app.db_engine import (  # noqa: E402
+    BattingSeasonStats,
+    Card,
+    Cardset,
+    Decision,
+    Event,
+    MlbPlayer,
+    Pack,
+    PackType,
+    PitchingSeasonStats,
+    Player,
+    ProcessedGame,
+    Rarity,
+    RefractorCardState,
+    RefractorCosmetic,
+    RefractorTierBoost,
+    RefractorTrack,
+    Roster,
+    RosterSlot,
+    ScoutClaim,
+    ScoutOpportunity,
+    StratGame,
+    StratPlay,
+    Team,
+)
 
 POSTGRES_HOST = os.environ.get("POSTGRES_HOST")
 _skip_no_pg = pytest.mark.skipif(
@@ -130,3 +165,172 @@ def test_auth_required(client, seeded_tracks):
     track_id = seeded_tracks[0]
     resp_single = client.get(f"/api/v2/refractor/tracks/{track_id}")
     assert resp_single.status_code == 401
+
+
+# ===========================================================================
+# SQLite-backed tests for T3-1: invalid card_type query parameter
+#
+# These tests run without a PostgreSQL connection.  They verify that the
+# card_type filter on GET /api/v2/refractor/tracks handles values that match
+# no known track (an unrecognised string, an empty string) gracefully: the
+# endpoint must return 200 with {"count": 0, "items": []}, not a 4xx/5xx.
+# ===========================================================================
+
+_track_api_db = SqliteDatabase(
+    "file:trackapitest?mode=memory&cache=shared",
+    uri=True,
+    pragmas={"foreign_keys": 1},
+)
+
+_TRACK_API_MODELS = [
+    Rarity,
+    Event,
+    Cardset,
+    MlbPlayer,
+    Player,
+    Team,
+    PackType,
+    Pack,
+    Card,
+    Roster,
+    RosterSlot,
+    StratGame,
+    StratPlay,
+    Decision,
+    ScoutOpportunity,
+    ScoutClaim,
+    BattingSeasonStats,
+    PitchingSeasonStats,
+    ProcessedGame,
+    RefractorTrack,
+    RefractorCardState,
+    RefractorTierBoost,
+    RefractorCosmetic,
+]
+
+
+@pytest.fixture(autouse=False)
+def setup_track_api_db():
+    """Bind track-API test models to shared-memory SQLite and create tables.
+
+    Inserts exactly two tracks (batter, sp) so the filter tests have a
+    non-empty table to query against — confirming that the WHERE predicate
+    excludes them rather than the table simply being empty.
+    """
+    _track_api_db.bind(_TRACK_API_MODELS)
+    _track_api_db.connect(reuse_if_open=True)
+    _track_api_db.create_tables(_TRACK_API_MODELS)
+
+    # Seed two real tracks so the table is not empty
+    RefractorTrack.get_or_create(
+        name="T3-1 Batter Track",
+        defaults=dict(
+            card_type="batter",
+            formula="pa + tb * 2",
+            t1_threshold=37,
+            t2_threshold=149,
+            t3_threshold=448,
+            t4_threshold=896,
+        ),
+    )
+    RefractorTrack.get_or_create(
+        name="T3-1 SP Track",
+        defaults=dict(
+            card_type="sp",
+            formula="ip + k",
+            t1_threshold=10,
+            t2_threshold=40,
+            t3_threshold=120,
+            t4_threshold=240,
+        ),
+    )
+
+    yield _track_api_db
+    _track_api_db.drop_tables(list(reversed(_TRACK_API_MODELS)), safe=True)
+
+
+def _build_track_api_app() -> FastAPI:
+    """Minimal FastAPI app containing only the refractor router for T3-1 tests."""
+    from app.routers_v2.refractor import router as refractor_router
+
+    app = FastAPI()
+
+    @app.middleware("http")
+    async def db_middleware(request: Request, call_next):
+        _track_api_db.connect(reuse_if_open=True)
+        return await call_next(request)
+
+    app.include_router(refractor_router)
+    return app
+
+
+@pytest.fixture
+def track_api_client(setup_track_api_db):
+    """FastAPI TestClient for the SQLite-backed T3-1 track filter tests."""
+    with TestClient(_build_track_api_app()) as c:
+        yield c
+
+
+# ---------------------------------------------------------------------------
+# T3-1a: card_type=foo (unrecognised value) returns empty list
+# ---------------------------------------------------------------------------
+
+
+def test_invalid_card_type_returns_empty_list(setup_track_api_db, track_api_client):
+    """GET /tracks?card_type=foo returns 200 with count=0, not a 4xx/5xx.
+
+    What: Query the track list with a card_type value ('foo') that matches
+    no row in refractor_track.  The table contains batter and sp tracks so
+    the result must be an empty list rather than a full list (which would
+    indicate the filter was ignored).
+
+    Why: The endpoint applies `WHERE card_type == card_type` when the
+    parameter is not None.  An unrecognised value is a valid no-match query
+    — the contract is an empty list, not a validation error.  Returning
+    a 422 Unprocessable Entity or 500 here would break clients that probe
+    for tracks by card type before knowing which types are registered.
+    """
+    resp = track_api_client.get(
+        "/api/v2/refractor/tracks?card_type=foo", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["count"] == 0, (
+        f"Expected count=0 for unknown card_type 'foo', got {data['count']}"
+    )
+    assert data["items"] == [], (
+        f"Expected empty items list for unknown card_type 'foo', got {data['items']}"
+    )
+
+
+# ---------------------------------------------------------------------------
+# T3-1b: card_type= (empty string) returns empty list
+# ---------------------------------------------------------------------------
+
+
+def test_empty_string_card_type_returns_empty_list(
+    setup_track_api_db, track_api_client
+):
+    """GET /tracks?card_type= (empty string) returns 200 with count=0.
+
+    What: Pass an empty string as the card_type query parameter.  No track
+    has card_type='' so the response must be an empty list with count=0.
+
+    Why: An empty string is not None — FastAPI will pass it through as ''
+    rather than treating it as an absent parameter.  The WHERE predicate
+    `card_type == ''` produces no matches, which is the correct silent
+    no-results behaviour.  This guards against regressions where an empty
+    string might be mishandled as a None/absent value and accidentally return
+    all tracks, or raise a server error.
+    """
+    resp = track_api_client.get(
+        "/api/v2/refractor/tracks?card_type=", headers=AUTH_HEADER
+    )
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["count"] == 0, (
+        f"Expected count=0 for empty card_type string, got {data['count']}"
+    )
+    assert data["items"] == [], (
+        f"Expected empty items list for empty card_type string, got {data['items']}"
+    )