diff --git a/database.py b/database.py
index f068feb..dbc1efa 100644
--- a/database.py
+++ b/database.py
@@ -691,7 +691,9 @@ class MotionDatabase:
                 return "tegen"
             if s_low in ("onthouden", "abstain", "abstained"):
                 return "onthouden"
-            if s_low in ("geen stem", "afwezig", "absent", "no vote"):
+            if s_low in ("geen stem", "no vote"):
+                return None  # user chose not to answer — skip entirely
+            if s_low in ("afwezig", "absent"):
                 return "afwezig"
             # already canonical?
             if s_low in ("voor", "tegen", "onthouden", "afwezig"):
diff --git a/tests/test_explorer_quiz.py b/tests/test_explorer_quiz.py
new file mode 100644
index 0000000..7e89d9a
--- /dev/null
+++ b/tests/test_explorer_quiz.py
@@ -0,0 +1,158 @@
+"""Tests for build_mp_quiz_tab and related quiz DB integration.
+
+Task 2.1 + Task 3.1: smoke test that the builder is exported and callable,
+plus an end-to-end simulation of the quiz matching logic via real temp DuckDB.
+"""
+
+import importlib
+from pathlib import Path
+
+import duckdb
+
+from database import MotionDatabase
+
+
+# ---------------------------------------------------------------------------
+# Helpers
+# ---------------------------------------------------------------------------
+
+
+def _create_motion(db: MotionDatabase, url: str, title: str, controversy: float = 0.5):
+    md = {
+        "title": title,
+        "description": title,
+        "date": "2023-01-01",
+        "policy_area": "test",
+        "voting_results": {},
+        "winning_margin": controversy,
+        "layman_explanation": f"Uitleg over {title}",
+        "url": url,
+    }
+    ok = db.insert_motion(md)
+    assert ok, f"insert_motion failed for {url}"
+    conn = duckdb.connect(db.db_path)
+    row = conn.execute("SELECT id FROM motions WHERE url = ?", (url,)).fetchone()
+    conn.close()
+    assert row is not None
+    return int(row[0])
+
+
+# ---------------------------------------------------------------------------
+# Task 2.1 — smoke test: builder exported and callable
+# ---------------------------------------------------------------------------
+
+
+def test_builder_exists():
+    """build_mp_quiz_tab must be importable from explorer and callable."""
+    mod = importlib.import_module("explorer")
+    assert hasattr(mod, "build_mp_quiz_tab"), "build_mp_quiz_tab not found in explorer"
+    assert callable(mod.build_mp_quiz_tab)
+
+
+# ---------------------------------------------------------------------------
+# Task 3.1 — end-to-end quiz matching simulation
+# ---------------------------------------------------------------------------
+
+
+def test_quiz_unique_match(tmp_path: Path):
+    """Full quiz flow: 6 motions, 4 MPs — pre-filled votes produce a unique match."""
+    db_path = str(tmp_path / "quiz_e2e.db")
+    db = MotionDatabase(db_path)
+
+    # 6 motions
+    mids = [_create_motion(db, f"http://qe{i}", f"Motion {i}") for i in range(6)]
+
+    # 4 MPs with distinct voting patterns
+    mpA = "Alpha, A."
+    mpB = "Beta, B."
+    mpC = "Gamma, G."
+    mpD = "Delta, D."
+
+    patterns = {
+        mpA: ["voor", "voor", "voor", "voor", "voor", "voor"],  # all voor
+        mpB: ["tegen", "tegen", "voor", "voor", "voor", "voor"],  # 2 tegen then 4 voor
+        mpC: ["voor", "tegen", "voor", "tegen", "voor", "tegen"],  # alternating
+        mpD: ["tegen", "tegen", "tegen", "tegen", "tegen", "voor"],  # mostly tegen
+    }
+
+    for idx, mid in enumerate(mids):
+        for mp, votes in patterns.items():
+            db.insert_mp_vote(mid, mp, votes[idx], "2023-01-01")
+
+    # User votes matching mpA exactly (all Voor)
+    user_votes = {mid: "Voor" for mid in mids}
+    results = db.match_mps_for_votes(user_votes, limit=50)
+
+    assert results, "Expected ranked results"
+    top = results[0]
+    assert top["mp_name"] == mpA
+    assert top["agreement_pct"] == 100.0
+
+    # Unique match: only mpA should be at 100%
+    top_matches = [r for r in results if r["agreement_pct"] == top["agreement_pct"]]
+    assert len(top_matches) == 1, f"Expected unique top match, got {top_matches}"
+
+
+def test_quiz_indistinguishable_mps(tmp_path: Path):
+    """When two MPs vote identically, both appear at the top with same agreement_pct."""
+    db_path = str(tmp_path / "quiz_indist.db")
+    db = MotionDatabase(db_path)
+
+    mids = [
+        _create_motion(db, f"http://ind{i}", f"Indist Motion {i}") for i in range(3)
+    ]
+
+    mpA = "Alice, A."
+    mpB = "Bob, B."
+
+    # Both vote identically
+    for mid in mids:
+        db.insert_mp_vote(mid, mpA, "voor", "2023-01-01")
+        db.insert_mp_vote(mid, mpB, "voor", "2023-01-01")
+
+    user_votes = {mid: "Voor" for mid in mids}
+    results = db.match_mps_for_votes(user_votes, limit=50)
+
+    assert len(results) == 2, "Both identical MPs should appear"
+    assert results[0]["agreement_pct"] == results[1]["agreement_pct"] == 100.0
+
+
+def test_quiz_discriminating_reduces_candidates(tmp_path: Path):
+    """After one discriminating question, candidate set should shrink."""
+    db_path = str(tmp_path / "quiz_disc.db")
+    db = MotionDatabase(db_path)
+
+    # 4 motions: motion0 splits mpA from mpB/mpC
+    mids = [_create_motion(db, f"http://disc{i}", f"Disc Motion {i}") for i in range(4)]
+
+    mpA = "Alpha, A."
+    mpB = "Beta, B."
+    mpC = "Gamma, G."
+
+    # motion0 splits; motions 1-3 they all agree
+    db.insert_mp_vote(mids[0], mpA, "voor", "2023-01-01")
+    db.insert_mp_vote(mids[0], mpB, "tegen", "2023-01-01")
+    db.insert_mp_vote(mids[0], mpC, "tegen", "2023-01-01")
+
+    for i in range(1, 4):
+        for mp in (mpA, mpB, mpC):
+            db.insert_mp_vote(mids[i], mp, "voor", "2023-01-01")
+
+    # All three agree on motions 1-3; choose_discriminating_motions should pick motion0
+    all_mps = [mpA, mpB, mpC]
+    chosen = db.choose_discriminating_motions(all_mps, excluded_motion_ids=[], k=1)
+    assert chosen[0] == mids[0], (
+        f"Expected motion {mids[0]} as discriminating, got {chosen}"
+    )
+
+    # After user answers Voor on motion0, only mpA should rank at 100%
+    user_votes = {mids[0]: "Voor"}
+    results = db.match_mps_for_votes(user_votes, limit=50)
+    top = results[0]
+    assert top["mp_name"] == mpA
+    assert top["agreement_pct"] == 100.0
+
+    # mpB and mpC should be at 0%
+    for r in results:
+        if r["mp_name"] in (mpB, mpC):
+            assert r["agreement_pct"] == 0.0
diff --git a/tests/test_match_mps.py b/tests/test_match_mps.py
new file mode 100644
index 0000000..56a4aea
--- /dev/null
+++ b/tests/test_match_mps.py
@@ -0,0 +1,207 @@
+import duckdb
+import json
+import os
+from pathlib import Path
+
+from database import MotionDatabase
+
+
+def _create_motion_and_get_id(
+    db: MotionDatabase, url: str, title: str, layman: str = "x"
+):
+    md = {
+        "title": title,
+        "description": title,
+        "date": "2023-01-01",
+        "policy_area": "test",
+        "voting_results": {},
+        "winning_margin": 0.5,
+        "layman_explanation": layman,
+        "url": url,
+    }
+    ok = db.insert_motion(md)
+    assert ok, "insert_motion failed"
+    conn = duckdb.connect(db.db_path)
+    row = conn.execute("SELECT id FROM motions WHERE url = ?", (url,)).fetchone()
+    conn.close()
+    assert row is not None, "couldn't find inserted motion"
+    return int(row[0])
+
+
+def test_match_mps_basic(tmp_path: Path):
+    db_path = str(tmp_path / "test_motions.db")
+    db = MotionDatabase(db_path)
+
+    # create 4 motions
+    mids = []
+    for i in range(1, 5):
+        mids.append(_create_motion_and_get_id(db, f"http://m{i}", f"Motion {i}"))
+
+    # MPs
+    mpA = "Alpha, A."
+    mpB = "Beta, B."
+    mpC = "Gamma, G."
+
+    # Voting patterns (motions 1..4)
+    # A: v v t v  (3/4)
+    # B: t t t t  (0/4)
+    # C: v v v v  (4/4)
+    votes = {
+        mpA: ["voor", "voor", "tegen", "voor"],
+        mpB: ["tegen", "tegen", "tegen", "tegen"],
+        mpC: ["voor", "voor", "voor", "voor"],
+    }
+
+    for idx, mid in enumerate(mids):
+        for mp_name, vlist in votes.items():
+            db.insert_mp_vote(
+                motion_id=mid,
+                mp_name=mp_name,
+                vote=vlist[idx],
+                date="2023-01-01",
+                party=None,
+            )
+
+    # User votes matching Gamma exactly
+    user_votes = {mids[0]: "Voor", mids[1]: "Voor", mids[2]: "Voor", mids[3]: "Voor"}
+
+    results = db.match_mps_for_votes(user_votes, limit=10)
+    assert results, "No results returned"
+
+    # Top candidate should be Gamma
+    top = results[0]
+    assert top["mp_name"] == mpC
+    assert top["matched"] == 4
+    assert top["overlap"] == 4
+    assert top["agreement_pct"] == 100.0
+
+    # Check Alpha is second with 3 matched
+    names = [r["mp_name"] for r in results]
+    assert mpA in names
+    a = next(r for r in results if r["mp_name"] == mpA)
+    assert a["matched"] == 3
+    assert a["overlap"] == 4
+    assert a["agreement_pct"] == 75.0
+
+
+def test_choose_discriminating_motions(tmp_path: Path):
+    db_path = str(tmp_path / "test_motions2.db")
+    db = MotionDatabase(db_path)
+
+    # create 3 motions
+    mids = []
+    for i in range(1, 4):
+        mids.append(_create_motion_and_get_id(db, f"http://d{i}", f"DMotion {i}"))
+
+    mpA = "Alice, A."
+    mpB = "Bob, B."
+    mpC = "Carol, C."
+
+    # Votes: motion1 splits A vs B/C
+    # motion1: A=voor, B=tegen, C=tegen
+    # motion2: all voor
+    # motion3: all tegen
+    db.insert_mp_vote(mids[0], mpA, "voor", "2023-01-01")
+    db.insert_mp_vote(mids[0], mpB, "tegen", "2023-01-01")
+    db.insert_mp_vote(mids[0], mpC, "tegen", "2023-01-01")
+
+    for mp in (mpA, mpB, mpC):
+        db.insert_mp_vote(mids[1], mp, "voor", "2023-01-01")
+        db.insert_mp_vote(mids[2], mp, "tegen", "2023-01-01")
+
+    candidates = [mpA, mpB, mpC]
+    chosen = db.choose_discriminating_motions(candidates, excluded_motion_ids=[], k=1)
+    assert chosen, "No discriminating motion returned"
+    # best splitter should be motion1 (mids[0])
+    assert chosen[0] == mids[0]
+
+
+def test_match_excludes_zero_overlap(tmp_path: Path):
+    """MPs who voted on none of the user's motions must not appear in results."""
+    db_path = str(tmp_path / "zo.db")
+    db = MotionDatabase(db_path)
+
+    mid1 = _create_motion_and_get_id(db, "http://zo1", "ZO Motion 1")
+    mid2 = _create_motion_and_get_id(db, "http://zo2", "ZO Motion 2")
+
+    mp_overlap = "Overlap, O."
+    mp_noshow = "Noshow, N."
+
+    db.insert_mp_vote(mid1, mp_overlap, "voor", "2023-01-01")
+    # mp_noshow only voted on mid2, not mid1
+    db.insert_mp_vote(mid2, mp_noshow, "voor", "2023-01-01")
+
+    results = db.match_mps_for_votes({mid1: "Voor"}, limit=10)
+    names = [r["mp_name"] for r in results]
+
+    assert mp_overlap in names, "mp_overlap should appear"
+    assert mp_noshow not in names, "mp_noshow had no overlap and must be excluded"
+
+
+def test_invalid_input_empty_user_votes(tmp_path: Path):
+    """Passing an empty dict must raise ValueError."""
+    db_path = str(tmp_path / "inv.db")
+    db = MotionDatabase(db_path)
+
+    import pytest
+
+    with pytest.raises(ValueError, match="non-empty"):
+        db.match_mps_for_votes({})
+
+
+def test_invalid_input_empty_candidates(tmp_path: Path):
+    """Passing empty candidates to choose_discriminating_motions must raise ValueError."""
+    db_path = str(tmp_path / "inv2.db")
+    db = MotionDatabase(db_path)
+
+    import pytest
+
+    with pytest.raises(ValueError):
+        db.choose_discriminating_motions([], excluded_motion_ids=[])
+
+
+def test_geen_stem_not_counted_in_overlap(tmp_path: Path):
+    """'Geen stem' user votes should be skipped (not counted in overlap or matched)."""
+    db_path = str(tmp_path / "gs.db")
+    db = MotionDatabase(db_path)
+
+    mid1 = _create_motion_and_get_id(db, "http://gs1", "GS Motion 1")
+    mid2 = _create_motion_and_get_id(db, "http://gs2", "GS Motion 2")
+
+    mpA = "Alpha, A."
+    db.insert_mp_vote(mid1, mpA, "voor", "2023-01-01")
+    db.insert_mp_vote(mid2, mpA, "voor", "2023-01-01")
+
+    # user says Geen stem on mid1 (skip), Voor on mid2
+    results = db.match_mps_for_votes({mid1: "Geen stem", mid2: "Voor"}, limit=10)
+    assert results, "Expected at least one result"
+    r = results[0]
+    # overlap should only be 1 (mid2 counted, mid1 skipped)
+    assert r["overlap"] == 1
+    assert r["matched"] == 1
+    assert r["agreement_pct"] == 100.0
+
+
+def test_choose_excluded_motions_respected(tmp_path: Path):
+    """Excluded motion ids must not be returned by choose_discriminating_motions."""
+    db_path = str(tmp_path / "excl.db")
+    db = MotionDatabase(db_path)
+
+    mid1 = _create_motion_and_get_id(db, "http://ex1", "EX Motion 1")
+    mid2 = _create_motion_and_get_id(db, "http://ex2", "EX Motion 2")
+
+    mpA = "Alice, A."
+    mpB = "Bob, B."
+
+    # mid1 splits them; mid2 they agree
+    db.insert_mp_vote(mid1, mpA, "voor", "2023-01-01")
+    db.insert_mp_vote(mid1, mpB, "tegen", "2023-01-01")
+    db.insert_mp_vote(mid2, mpA, "voor", "2023-01-01")
+    db.insert_mp_vote(mid2, mpB, "voor", "2023-01-01")
+
+    # Exclude mid1 — only mid2 is available, should return mid2
+    chosen = db.choose_discriminating_motions(
+        [mpA, mpB], excluded_motion_ids=[mid1], k=1
+    )
+    assert mid1 not in chosen, "Excluded motion must not be returned"
+    assert mid2 in chosen, "mid2 should be chosen as only available motion"