ludofischer · Sep 30, 2026 · Sep 30, 2026
diff --git a/test/helpers/benchmark-artifact.js b/test/helpers/benchmark-artifact.js
@@ -1,5 +1,6 @@
 /* oxlint-disable no-bitwise */
 import {
+  CORPUS_INTERVAL_METHOD,
   DECISION_CONFIG_VERSION,
   DECISION_INTERVAL_METHOD,
   PRECISION_METHOD,
@@ -26,6 +27,39 @@ export const SYNTHETIC_DECISION_CONFIG = {
   intervalMethod: DECISION_INTERVAL_METHOD,
 };
 
+export const CORPUS_DECISION_CONFIG = {
+  ...SYNTHETIC_DECISION_CONFIG,
+  warmupMinimum: 0,
+  warmupMaximum: 0,
+  measuredBatchCount: 6,
+  intervalMethod: CORPUS_INTERVAL_METHOD,
+  replicates: 20,
+  batches: 6,
+  calibrationOrderBalanced: true,
+};
+
+const CORPUS_CATEGORIES = [
+  'accepted',
+  'both-failed',
+  'known-divergence',
+  'malformed-input',
+  'parser-rejected',
+  'reference-rejected',
+  'unexpected-divergence',
+];
+
+/** Correctness block for a corpus artifact with two accepted inputs. */
+export function corpusCorrectness() {
+  return {
+    accepted: 2,
+    counts: Object.fromEntries(
+      CORPUS_CATEGORIES.map((c) => [c, c === 'accepted' ? 2 : 0])
+    ),
+    categoryHashes: Object.fromEntries(CORPUS_CATEGORIES.map((c) => [c, c])),
+    inputHash: 'inputs',
+  };
+}
+
 /**
  * Build a parser artifact from already-generated observations. `rows` contains
  * one complete independent block per item, with baseline and candidate arrays

diff --git a/test/helpers/numeric.js b/test/helpers/numeric.js
@@ -0,0 +1,6 @@
+// Read a number out of serialized CSS such as `calc(1.5)` or `-2`.
+export const scalarText = (text) =>
+  text.startsWith('calc(') && text.endsWith(')')
+    ? text.slice('calc('.length, -1)
+    : text;
+export const numeric = (text) => Number.parseFloat(scalarText(text));
diff --git a/test/helpers/parse-source.js b/test/helpers/parse-source.js
@@ -0,0 +1,9 @@
+// Parse CSS source over its full token range with the production parser.
+import { tokenize } from '@csstools/css-tokenizer';
+import { indexBlocks } from '../../src/lib/block-index.js';
+import { parse } from '../../src/lib/parser.js';
+
+export const parseSource = (css) => {
+  const tokens = tokenize({ css });
+  return parse(tokens, 0, tokens.length, indexBlocks(tokens));
+};
diff --git a/test/helpers/testValue.js b/test/helpers/testValue.js
@@ -19,3 +19,24 @@ export function testValue(fixture, expected, opts = {}) {
     assert.strictEqual(result.css, expected);
   };
 }
+
+export function testCss(fixture, expected, opts = {}) {
+  return async () => {
+    const result = await postcss(reduceCalc(opts)).process(
+      fixture,
+      postcssOpts
+    );
+    assert.strictEqual(result.css, expected);
+  };
+}
+
+export function testCssDoesNotThrow(fixture, expected, opts = {}) {
+  return async () => {
+    const result = await postcss(reduceCalc(opts)).process(
+      fixture,
+      postcssOpts
+    );
+    assert.strictEqual(result.css, expected);
+    assert.strictEqual(result.warnings().length, 0);
+  };
+}
diff --git a/test/index-cases.test.cjs b/test/index-cases.test.cjs
@@ -1,34 +1,11 @@
 'use strict';
 
 const { describe, test } = require('node:test');
-const assert = require('node:assert/strict');
-const postcss = require('postcss');
-const reduceCalc = (opts = {}) => require('../src/index.js')(opts);
-const { testValue } = require('./helpers/testValue.js');
-
-const postcssOpts = { from: undefined };
-
-function testCss(fixture, expected, opts = {}) {
-  return async () => {
-    const result = await postcss(reduceCalc(opts)).process(
-      fixture,
-      postcssOpts
-    );
-    assert.strictEqual(result.css, expected);
-  };
-}
-
-function testCssDoesNotThrow(fixture, expected, opts = {}) {
-  return async () => {
-    const result = await postcss(reduceCalc(opts)).process(
-      fixture,
-      postcssOpts
-    );
-    assert.strictEqual(result.css, expected);
-    const warnings = result.warnings();
-    assert.strictEqual(warnings.length, 0);
-  };
-}
+const {
+  testValue,
+  testCss,
+  testCssDoesNotThrow,
+} = require('./helpers/testValue.js');
 
 describe('CSS custom properties', () => {
   test(

diff --git a/test/index-edge-cases.test.cjs b/test/index-edge-cases.test.cjs
@@ -1,24 +1,8 @@
 'use strict';
 
 const { describe, test } = require('node:test');
-const assert = require('node:assert/strict');
-const postcss = require('postcss');
-const reduceCalc = (opts = {}) => require('../src/index.js')(opts);
-const { testValue } = require('./helpers/testValue.js');
-
-const postcssOpts = { from: undefined };
-
-function testCssDoesNotThrow(fixture, expected, opts = {}) {
-  return async () => {
-    const result = await postcss(reduceCalc(opts)).process(
-      fixture,
-      postcssOpts
-    );
-    assert.strictEqual(result.css, expected);
-    const warnings = result.warnings();
-    assert.strictEqual(warnings.length, 0);
-  };
-}
+const { testValue, testCssDoesNotThrow } = require('./helpers/testValue.js');
+
 describe('Throw', () => {
   test(
     'should not throw an exception when unknow function exist in calc',

diff --git a/test/index-options.test.cjs b/test/index-options.test.cjs
@@ -1,22 +1,7 @@
 'use strict';
 
 const { describe, test } = require('node:test');
-const assert = require('node:assert/strict');
-const postcss = require('postcss');
-const reduceCalc = (opts = {}) => require('../src/index.js')(opts);
-const { testValue } = require('./helpers/testValue.js');
-
-const postcssOpts = { from: undefined };
-
-function testCss(fixture, expected, opts = {}) {
-  return async () => {
-    const result = await postcss(reduceCalc(opts)).process(
-      fixture,
-      postcssOpts
-    );
-    assert.strictEqual(result.css, expected);
-  };
-}
+const { testValue, testCss } = require('./helpers/testValue.js');
 
 describe('Discard zero values', () => {
   test(

diff --git a/test/property/algebraic-exponential.test.js b/test/property/algebraic-exponential.test.js
@@ -11,16 +11,12 @@ import { describe, test } from 'node:test';
 import fc from 'fast-check';
 import { simplify } from '../../src/lib/simplify.js';
 import { serialize } from '../../src/lib/serialize.js';
+import { numeric } from '../helpers/numeric.js';
 import { call, num } from '../../src/lib/node.js';
 
 const NUM_RUNS = 500;
 
 const out = (n) => serialize(simplify(n), { precision: 10 });
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
 
 // --- pow / sqrt / log / exp / hypot laws (§10.5) ----------------------
 test('law: pow(x, 1) ≡ x for finite x', () => {

diff --git a/test/property/algebraic-mod-rem.test.js b/test/property/algebraic-mod-rem.test.js
@@ -11,16 +11,12 @@ import { describe, test } from 'node:test';
 import fc from 'fast-check';
 import { simplify } from '../../src/lib/simplify.js';
 import { serialize } from '../../src/lib/serialize.js';
+import { numeric } from '../helpers/numeric.js';
 import { call, num, ident } from '../../src/lib/node.js';
 
 const NUM_RUNS = 500;
 
 const out = (n) => serialize(simplify(n), { precision: 10 });
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
 
 // Finite, non-zero numeric leaf — domain for most laws.
 const finiteNum = fc.integer({ min: -1000, max: 1000 }).map(num);

diff --git a/test/property/algebraic-round.test.js b/test/property/algebraic-round.test.js
@@ -11,16 +11,12 @@ import { describe, test } from 'node:test';
 import fc from 'fast-check';
 import { simplify } from '../../src/lib/simplify.js';
 import { serialize } from '../../src/lib/serialize.js';
+import { numeric } from '../helpers/numeric.js';
 import { call, num, ident } from '../../src/lib/node.js';
 
 const NUM_RUNS = 500;
 
 const out = (n) => serialize(simplify(n), { precision: 10 });
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
 
 // Finite, non-zero numeric leaf — domain for most laws.
 const finiteNum = fc.integer({ min: -1000, max: 1000 }).map(num);

diff --git a/test/property/algebraic-sign.test.js b/test/property/algebraic-sign.test.js
@@ -11,16 +11,12 @@ import { describe, test } from 'node:test';
 import fc from 'fast-check';
 import { simplify } from '../../src/lib/simplify.js';
 import { serialize } from '../../src/lib/serialize.js';
+import { numeric, scalarText } from '../helpers/numeric.js';
 import { call, num, dim } from '../../src/lib/node.js';
 
 const NUM_RUNS = 500;
 
 const out = (n) => serialize(simplify(n), { precision: 10 });
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
 
 // Finite, non-zero numeric leaf — domain for most laws.
 const finiteNum = fc.integer({ min: -1000, max: 1000 }).map(num);

diff --git a/test/property/algebraic-trigonometry.test.js b/test/property/algebraic-trigonometry.test.js
@@ -11,16 +11,12 @@ import { describe, test } from 'node:test';
 import fc from 'fast-check';
 import { simplify } from '../../src/lib/simplify.js';
 import { serialize } from '../../src/lib/serialize.js';
+import { numeric } from '../helpers/numeric.js';
 import { call, num } from '../../src/lib/node.js';
 
 const NUM_RUNS = 500;
 
 const out = (n) => serialize(simplify(n), { precision: 10 });
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
 
 // --- trig laws (§10.4) ---------------------------------------------------
 //

diff --git a/test/property/naive-exponential.test.js b/test/property/naive-exponential.test.js
@@ -10,23 +10,9 @@
 // random gen to roll them.
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { tokenize } from '@csstools/css-tokenizer';
-import { indexBlocks } from '../../src/lib/block-index.js';
-import { parse } from '../../src/lib/parser.js';
-import { simplify } from '../../src/lib/simplify.js';
-import { serialize } from '../../src/lib/serialize.js';
-const out = (s) => {
-  const tokens = tokenize({ css: s });
-  return serialize(
-    simplify(parse(tokens, 0, tokens.length, indexBlocks(tokens))),
-    { precision: 10 }
-  );
-};
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
+import { out as pipeline } from '../helpers/out.js';
+import { numeric } from '../helpers/numeric.js';
+const out = (s) => pipeline(s, { precision: 10 });
 // --- §10.5 oracle rows for pow / sqrt / exp / log / hypot --------------
 const POW_INPUTS = [
   [2, 3],

diff --git a/test/property/naive-stepped.test.js b/test/property/naive-stepped.test.js
@@ -10,23 +10,20 @@
 // random gen to roll them.
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
-import { tokenize } from '@csstools/css-tokenizer';
-import { indexBlocks } from '../../src/lib/block-index.js';
-import { parse } from '../../src/lib/parser.js';
-import { simplify } from '../../src/lib/simplify.js';
-import { serialize } from '../../src/lib/serialize.js';
-const out = (s) => {
-  const tokens = tokenize({ css: s });
-  return serialize(
-    simplify(parse(tokens, 0, tokens.length, indexBlocks(tokens))),
-    { precision: 10 }
-  );
-};
-const scalarText = (text) =>
-  text.startsWith('calc(') && text.endsWith(')')
-    ? text.slice('calc('.length, -1)
-    : text;
-const numeric = (text) => Number.parseFloat(scalarText(text));
+import { out as pipeline } from '../helpers/out.js';
+import { numeric } from '../helpers/numeric.js';
+const out = (s) => pipeline(s, { precision: 10 });
+// NaN must match NaN; otherwise allow tiny FP drift between algorithm shapes.
+function assertAgrees(expected, got) {
+  if (Number.isNaN(expected)) {
+    assert.ok(Number.isNaN(got), `expected NaN, got ${got}`);
+  } else {
+    assert.ok(
+      Math.abs(expected - got) < 1e-9,
+      `naive=${expected}, prod=${got}`
+    );
+  }
+}
 // --- Naive reference impls ----------------------------------------------
 //
 // These use a *different* algorithmic shape from `simplify.ts`:
@@ -134,15 +131,7 @@ for (const row of rows) {
       const expected = naiveRound(strategy, row.a, row.b);
       const got = numeric(out(`round(${strategy}, ${row.a}, ${row.b})`));
       // NaN === NaN check via Object.is.
-      if (Number.isNaN(expected)) {
-        assert.ok(Number.isNaN(got), `expected NaN, got ${got}`);
-      } else {
-        // Allow tiny FP drift between algorithm shapes.
-        assert.ok(
-          Math.abs(expected - got) < 1e-9,
-          `naive=${expected}, prod=${got}`
-        );
-      }
+      assertAgrees(expected, got);
     });
   }
 }
@@ -153,26 +142,12 @@ for (const row of rows) {
   test(`oracle: mod(${row.a}, ${row.b}) [${row.desc}]`, () => {
     const expected = naiveMod(row.a, row.b);
     const got = numeric(out(`mod(${row.a}, ${row.b})`));
-    if (Number.isNaN(expected)) {
-      assert.ok(Number.isNaN(got), `expected NaN, got ${got}`);
-    } else {
-      assert.ok(
-        Math.abs(expected - got) < 1e-9,
-        `naive=${expected}, prod=${got}`
-      );
-    }
+    assertAgrees(expected, got);
   });
   test(`oracle: rem(${row.a}, ${row.b}) [${row.desc}]`, () => {
     const expected = naiveRem(row.a, row.b);
     const got = numeric(out(`rem(${row.a}, ${row.b})`));
-    if (Number.isNaN(expected)) {
-      assert.ok(Number.isNaN(got), `expected NaN, got ${got}`);
-    } else {
-      assert.ok(
-        Math.abs(expected - got) < 1e-9,
-        `naive=${expected}, prod=${got}`
-      );
-    }
+    assertAgrees(expected, got);
   });
 }
 // --- abs / sign — small but covers signed zero -------------------------