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+// Unit tests for the color-families model (app-core.js): grouping a flat palette
+// into hue families, regenerating a family's ramp, ranking members by lightness,
+// and planning the assignment re-point across a regenerate. Phase 1 of the
+// color-families spec. Pure, no DOM. Run: node --test scripts/theme-studio/
+
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { familiesFromPalette, regenFamily, rankByLightness, stepRepointPlan, sortFamilies } from './app-core.js';
+import { oklch2hex, srgb2oklab, oklab2oklch } from './colormath.js';
+
+// Build a palette entry at a controlled OKLCH hue so clustering is deterministic.
+const at = (L, C, H, name) => [oklch2hex(L, C, H).hex, name || ('c' + H)];
+
+// --- familiesFromPalette ----------------------------------------------------
+
+test('familiesFromPalette: Normal — separated hues split into one family each', () => {
+  const pal = [at(0.6, 0.1, 30, 'red'), at(0.6, 0.1, 150, 'green'), at(0.6, 0.1, 270, 'blue')];
+  const { ground, families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  assert.equal(families.length, 3, 'three separated hues -> three families');
+  assert.equal(ground.length, 2, 'ground strip carries bg and fg');
+  for (const f of families) assert.equal(f.members.length, 1);
+});
+
+test('familiesFromPalette: Boundary — near hues at the same lightness stay one family', () => {
+  const pal = [at(0.55, 0.1, 250, 'b1'), at(0.6, 0.1, 256, 'b2')];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  assert.equal(families.length, 1, 'a near hue-pair is one family');
+  assert.equal(families[0].members.length, 2);
+});
+
+test('familiesFromPalette: Boundary — well-separated hues split', () => {
+  const pal = [at(0.6, 0.1, 255, 'b'), at(0.6, 0.1, 200, 'c')];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  assert.equal(families.length, 2);
+});
+
+test('familiesFromPalette: Boundary — an intermediate chain does not merge gold into green', () => {
+  // complete linkage requires every cross-pair compatible, so the far endpoints (90° vs 150°) keep the chain from fusing
+  const pal = [at(0.7, 0.1, 90, 'gold'), at(0.65, 0.1, 110, 'olive'), at(0.6, 0.1, 130, 'yg'), at(0.55, 0.1, 150, 'green')];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  assert.equal(families.length, 2, 'not one chained family');
+});
+
+test('familiesFromPalette: Boundary — a pale tint keeps its hue while a mid gray goes neutral', () => {
+  const paleBlue = oklch2hex(0.9, 0.03, 255).hex;   // light, faint -> still blue
+  const midGray = oklch2hex(0.6, 0.025, 100).hex;   // mid, faint -> reads neutral
+  const { families } = familiesFromPalette([[paleBlue, 'paleblue'], [midGray, 'graytone']], { bg: '#000000', fg: '#ffffff' });
+  const neutral = families.find(f => f.neutral);
+  assert.ok(neutral && neutral.members.some(m => m.name === 'graytone'), 'mid faint color is neutral');
+  assert.ok(families.some(f => !f.neutral && f.members.some(m => m.name === 'paleblue')), 'pale tint stays chromatic');
+});
+
+test('familiesFromPalette: Boundary — near-neutral colors form a separate family', () => {
+  const pal = [at(0.6, 0.1, 250, 'blue'), at(0.5, 0.004, 250, 'gray')]; // gray below the chroma threshold
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  const neutral = families.find(f => f.neutral);
+  assert.ok(neutral, 'a neutral family exists');
+  assert.ok(neutral.members.some(m => m.name === 'gray'));
+  assert.ok(families.some(f => !f.neutral && f.members.some(m => m.name === 'blue')));
+});
+
+// --- real-palette grouping (the hard cases the color-sorting reviews measured) ---
+
+// The contested region of the distinguished/sterling palette: the gold ramp and
+// the olive ramp whose hue ranges nearly touch but whose mid-tones are far apart.
+const GOLD = [['#875f00', 'yellow-2'], ['#8e784c', 'yellow-1'], ['#d7af5f', 'yellow'], ['#ffd75f', 'yellow+1']];
+const OLIVE = [['#646d14', 'green-2'], ['#869038', 'green-1'], ['#a4ac64', 'green'], ['#ccc768', 'green+1']];
+const famOf = (families, name) => families.find(f => f.members.some(m => m.name === name));
+
+test('familiesFromPalette: Normal — the gold and olive ramps separate', () => {
+  const { families } = familiesFromPalette([...GOLD, ...OLIVE], { bg: '#000000', fg: '#ffffff' });
+  const gold = famOf(families, 'yellow'), olive = famOf(families, 'green');
+  assert.notEqual(gold, olive, 'gold and olive are different families');
+  assert.ok(!gold.members.some(m => m.name.startsWith('green')), 'gold family has no greens');
+  assert.ok(!olive.members.some(m => m.name.startsWith('yellow')), 'olive family has no yellows');
+});
+
+test('familiesFromPalette: Normal — the blue ramp stays whole despite pale-tint hue drift', () => {
+  // blue (H 252), blue+1 (H 231), blue+2 (H 272): low-chroma pale tints swing in hue but belong together
+  const pal = [['#67809c', 'blue'], ['#b2c3cc', 'blue+1'], ['#d9e2ff', 'blue+2']];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  const blue = famOf(families, 'blue');
+  assert.equal(blue.members.length, 3, 'all three blues in one family');
+});
+
+test('familiesFromPalette: Boundary — pale warm grays and pure white read as neutral', () => {
+  const pal = [['#b4b1a2', 'gray+1'], ['#d0cbc0', 'gray+2'], ['#ffffff', 'white'], ['#67809c', 'blue']];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#f0fef0' }); // fg distinct from the white swatch
+  const neutral = families.find(f => f.neutral);
+  for (const n of ['gray+1', 'gray+2', 'white']) assert.ok(neutral.members.some(m => m.name === n), n + ' is neutral');
+  assert.ok(famOf(families, 'blue') && !famOf(families, 'blue').neutral, 'blue stays chromatic');
+});
+
+test('familiesFromPalette: Boundary — a vivid accent stays out of a soft same-hue family', () => {
+  // intense-red (C 0.246) vs red (C 0.120) at similar lightness: the chroma clause keeps them apart
+  const pal = [['#ff2a00', 'intense-red'], ['#d47c59', 'red'], ['#a7502d', 'red-1']];
+  const { families } = familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' });
+  assert.notEqual(famOf(families, 'intense-red'), famOf(families, 'red'), 'intense-red is its own family');
+});
+
+test('familiesFromPalette: Boundary — grouping is independent of palette order', () => {
+  const base = [...GOLD, ...OLIVE, ['#67809c', 'blue'], ['#b2c3cc', 'blue+1'], ['#969385', 'gray']];
+  const key = pal => familiesFromPalette(pal, { bg: '#000000', fg: '#ffffff' }).families
+    .map(f => f.members.map(m => m.name).sort().join(',')).sort().join(' | ');
+  const ref = key(base);
+  for (const seed of [1, 2, 3]) { // a few deterministic shuffles
+    const shuffled = base.map((e, i) => [e, ((i + 1) * seed * 7) % base.length]).sort((a, b) => a[1] - b[1]).map(x => x[0]);
+    assert.equal(key(shuffled), ref, 'shuffle ' + seed + ' yields the same grouping');
+  }
+});
+
+test('familiesFromPalette: Boundary — ground hex absent from the palette still forms the strip', () => {
+  const pal = [at(0.6, 0.1, 250, 'blue')];
+  const { ground } = familiesFromPalette(pal, { bg: '#0d0b0a', fg: '#f0fef0' });
+  assert.equal(ground.length, 2);
+  assert.ok(ground.some(g => g.hex.toLowerCase() === '#0d0b0a' && g.role === 'bg'));
+  assert.ok(ground.some(g => g.role === 'fg'));
+});
+
+test('familiesFromPalette: Boundary — a chip at a ground hex is not duplicated into a family', () => {
+  const pal = [['#0d0b0a', 'ground'], at(0.6, 0.1, 250, 'blue')];
+  const { ground, families } = familiesFromPalette(pal, { bg: '#0d0b0a', fg: '#f0fef0' });
+  assert.ok(ground.some(g => g.hex.toLowerCase() === '#0d0b0a'));
+  assert.ok(!families.some(f => f.members.some(m => m.hex.toLowerCase() === '#0d0b0a')), 'ground chip stays out of families');
+});
+
+// --- regenFamily ------------------------------------------------------------
+
+test('regenFamily: Normal — n steps each side plus the base, ordered by offset', () => {
+  const r = regenFamily('#67809c', 2);
+  assert.equal(r.members.length, 5);
+  assert.deepEqual(r.members.map(m => m.offset), [-2, -1, 0, 1, 2]);
+  assert.equal(r.members.find(m => m.offset === 0).hex, '#67809c');
+});
+
+test('regenFamily: Boundary — n=0 is the base alone, no ramp() clamp to 1', () => {
+  const r = regenFamily('#67809c', 0);
+  assert.deepEqual(r.members, [{ hex: '#67809c', offset: 0, clamped: false }]);
+});
+
+test('regenFamily: Error — a malformed base returns a structured bad-hex', () => {
+  assert.deepEqual(regenFamily('nope', 2), { members: [], error: 'bad-hex' });
+});
+
+// --- rankByLightness --------------------------------------------------------
+
+test('rankByLightness: Normal — offsets are signed distance from the base by lightness', () => {
+  const members = regenFamily('#67809c', 2).members.map(m => m.hex);
+  const ranked = rankByLightness(members, '#67809c');
+  const base = ranked.find(m => m.hex === '#67809c');
+  assert.equal(base.offset, 0);
+  const sorted = [...ranked].sort((a, b) => a.offset - b.offset);
+  assert.deepEqual(sorted.map(m => m.offset), [-2, -1, 0, 1, 2]);
+});
+
+test('rankByLightness: Boundary — a base not among the members ranks by nearest lightness', () => {
+  const members = ['#222222', '#888888', '#dddddd'];
+  const ranked = rankByLightness(members, '#8a8a8a'); // near the mid member
+  const mid = ranked.find(m => m.hex === '#888888');
+  assert.equal(mid.offset, 0, 'nearest-lightness member is the base rank');
+});
+
+// --- stepRepointPlan --------------------------------------------------------
+
+test('stepRepointPlan: Normal — surviving offsets map old->new, changed hex only', () => {
+  const oldR = [{ hex: '#111111', offset: -1 }, { hex: '#222222', offset: 0 }, { hex: '#333333', offset: 1 }];
+  const neu = [{ hex: '#111111', offset: -1 }, { hex: '#aaaaaa', offset: 0 }, { hex: '#444444', offset: 1 }];
+  const { map, removed } = stepRepointPlan(oldR, neu);
+  assert.deepEqual(removed, []);
+  assert.deepEqual(map, [['#222222', '#aaaaaa'], ['#333333', '#444444']]); // -1 unchanged, skipped
+});
+
+test('stepRepointPlan: Boundary — an offset with no new counterpart is removed, not repointed', () => {
+  const oldR = [{ hex: '#000033', offset: -3 }, { hex: '#222222', offset: 0 }];
+  const neu = [{ hex: '#222222', offset: 0 }]; // count dropped, -3 gone
+  const { map, removed } = stepRepointPlan(oldR, neu);
+  assert.deepEqual(map, []);
+  assert.deepEqual(removed, ['#000033']);
+});
+
+// --- sortFamilies -----------------------------------------------------------
+
+const fam = (baseHex, neutral, members) => ({ base: baseHex, neutral: !!neutral, members: (members || [baseHex]).map(h => ({ hex: h, name: h })) });
+
+test('sortFamilies: Normal — chromatic families order by base hue', () => {
+  const fams = [fam(oklch2hex(0.6, 0.1, 270).hex), fam(oklch2hex(0.6, 0.1, 30).hex), fam(oklch2hex(0.6, 0.1, 150).hex)];
+  const sorted = sortFamilies(fams);
+  const hues = sorted.map(f => Math.round(oklab2oklch(srgb2oklab(f.base)).H));
+  for (let i = 1; i < hues.length; i++) assert.ok(hues[i] > hues[i - 1], 'ascending hue: ' + hues.join(','));
+});
+
+test('sortFamilies: Boundary — neutral families pin ahead of chromatic ones', () => {
+  const sorted = sortFamilies([fam(oklch2hex(0.6, 0.1, 200).hex, false), fam('#808080', true)]);
+  assert.equal(sorted[0].neutral, true, 'neutral first');
+  assert.equal(sorted[1].neutral, false);
+});
+
+test('sortFamilies: Normal — members within a family sort dark to light', () => {
+  const members = ['#dddddd', '#222222', '#888888'];
+  const sorted = sortFamilies([fam(oklch2hex(0.6, 0.1, 200).hex, false, members)]);
+  const ls = sorted[0].members.map(m => oklab2oklch(srgb2oklab(m.hex)).L);
+  for (let i = 1; i < ls.length; i++) assert.ok(ls[i] > ls[i - 1], 'ascending lightness');
+});
+
+test('sortFamilies: Boundary — order is (hue, then lightness); a hue tie falls to lightness', () => {
+  const bases = [oklch2hex(0.6, 0.1, 200).hex, oklch2hex(0.5, 0.1, 200).hex, oklch2hex(0.6, 0.1, 40).hex];
+  const sorted = sortFamilies(bases.map(b => fam(b, false)));
+  const key = h => { const c = oklab2oklch(srgb2oklab(h)); return [Math.round(c.H), c.L]; };
+  for (let i = 1; i < sorted.length; i++) {
+    const [h0, l0] = key(sorted[i - 1].base), [h1, l1] = key(sorted[i].base);
+    assert.ok(h0 < h1 || (h0 === h1 && l0 <= l1), `order at ${i}: hue ${h0}/${h1} L ${l0.toFixed(3)}/${l1.toFixed(3)}`);
+  }
+});