auditing-typescript-tests

name	auditing-typescript-tests
description	ALWAYS invoke this skill when auditing tests for TypeScript or after writing tests. NEVER use auditing-typescript for test code.

TypeScript-specific test audit. Extends /auditing-tests with TypeScript supplements for each evidence property: coupling, falsifiability, alignment, coverage.

Read /auditing-tests first — it defines the 4-property evidence model and ordered workflow. This skill adds only what is TypeScript-specific.

<quick_start>

PREREQUISITE: Read /auditing-tests and its evidence model before auditing.

1. Run the /auditing-tests workflow: load context → map assertions → audit coupling → falsifiability → alignment → coverage → verdict
2. At each property step, apply the TypeScript supplement below
3. First property failure = REJECT (skip remaining properties for that assertion)

TypeScript filename conventions for assertion-to-test mapping:

Level	Filename suffix	Example
1	.unit.test.ts	uart-tx.unit.test.ts
2	.integration.test.ts	uart-tx.integration.test.ts
3	.e2e.test.ts	uart-tx.e2e.test.ts

</quick_start>

<essential_principles>

Follow the four principles from /auditing-tests: COUPLING FIRST, RUN COVERAGE DON'T GUESS, NO MECHANICAL DETECTION, BINARY VERDICT.

NO CODE QUALITY CHECKS.

Type safety (as any, @ts-ignore), return types, test organization, import style — these are linting concerns enforced by /standardizing-typescript, tsc strict mode, and ESLint. The auditor evaluates evidence quality only. A test with perfect TypeScript quality and zero evidentiary value must be REJECTED. A test with sloppy types but genuine evidence of spec fulfillment is not rejected by this audit.

</essential_principles>

<typescript_supplements>

Apply these at the corresponding step of the /auditing-tests workflow.

TypeScript import classification:

Import pattern	Classification
import { describe, expect, it } from "vitest"	Framework — does not count
import { z } from "zod"	Library — does not count
import type { Config } from "../src/config"	Type-only — does not count
import { parseConfig } from "../src/config"	Codebase (production) — counts
import { parseConfig } from "@/config"	Codebase (production alias) — counts
import { ConfigTestHarness } from "@testing/harnesses"	Codebase (test infra) — counts

Production code vs test harnesses — both are codebase imports:

Import target	Correct pattern	Classification
Production module	from "@/config"	Direct coupling
Test harness	from "@testing/harnesses"	Indirect coupling
Co-located test helper	from "./helpers"	Indirect coupling

Test harnesses wrap production modules, so they provide indirect coupling. When a test imports a harness, follow the chain: verify the harness itself has direct coupling to the module the assertion is about. If the harness is also a tautology, the coupling chain is broken.

Deep relative imports to test infrastructure are a red flag:

// ❌ Red flag — deep relative to test infra
import { ConfigTestHarness } from "../../../../../../tests/harnesses";
// Likely correct but fragile — verify the harness has real coupling

// ✅ Correct — path alias to test infra
import { ConfigTestHarness } from "@testing/harnesses";

Deep relative imports (../../../) are not themselves a coupling failure — the audit cares whether the import ultimately reaches the module under test, not the path style. But deep relative imports to test infrastructure signal the test may be importing a shared harness that wraps a different module than the assertion targets. Always trace the chain.

Type-only imports are not coupling. import type is erased at runtime — the test has zero runtime dependency on the module. If all codebase imports are import type, the test is a tautology.

Barrel re-exports can mask false coupling. If the test imports from an index.ts barrel file, verify the specific export used is the one the assertion is about — not a sibling export from the same barrel.

// Assertion is about parseConfig, but test uses validateConfig from same barrel
import { validateConfig } from "../src";
// parseConfig is also exported from "../src" but never called → false coupling

TypeScript mocking patterns that sever coupling:

// Coupling severed — real module never runs
import { database } from "../src/database";
vi.mock("../src/database", () => ({ query: vi.fn() }));

// Coupling severed — method intercepted
vi.spyOn(service, "process").mockReturnValue(fakeResult);

// Coupling severed — jest equivalent
jest.mock("../src/database");
jest.spyOn(service, "process").mockImplementation(() => fakeResult);

Legitimate alternatives mapped to /testing exceptions:

Exception	TypeScript pattern	Why coupling maintained
1. Failure modes	Class implementing interface, throws error	Tests error handling of real integration
2. Interaction protocols	Class with call-recording array	Tests call sequence against real interface
3. Time/concurrency	vi.useFakeTimers()	Tests timing logic with real code
4. Safety	Class that records but doesn't execute	Tests intent without destructive effects
5. Combinatorial cost	Configurable class mirroring real behavior	Tests breadth with real-shaped data
6. Observability	Class capturing request details	Tests details real system hides
7. Contract testing	Stub validated against schema	Tests serialization against real contract

For each test double found:

1. Identify which exception applies (must be one of the 7)
2. Verify the double is a class/object implementing an interface — not vi.mock/vi.spyOn
3. If vi.mock or vi.spyOn is used → coupling is severed → REJECT

Property-based testing via fast-check is required for specific assertion types:

Code type	Required property	Framework
Parsers	parse(format(x)) == x	fast-check / fc.assert
Serialization	decode(encode(x)) == x	fast-check / fc.assert
Mathematical operations	Algebraic properties	fast-check / fc.assert
Complex algorithms	Invariant preservation	fast-check / fc.assert

If the spec assertion describes a Property-type claim about a parser, serializer, or math operation, and the test uses only example-based assertions:

REJECT — "misaligned: Property assertion requires property-based test strategy."

// ❌ REJECT: Parser assertion with only example-based test
it("parses simple JSON", () => {
  const result = parse("{\"key\": \"value\"}");
  expect(result).toEqual({ key: "value" });
});
// Missing: fc.assert + roundtrip property

// ✅ PASS: Meaningful roundtrip property
it("roundtrips valid values", () => {
  fc.assert(
    fc.property(validJsonArbitrary(), (value) => {
      expect(parse(format(value))).toEqual(value);
    }),
  );
});

Verify property quality — fc.assert that only checks "doesn't throw" is not a meaningful property:

// ❌ REJECT: Trivial property (only tests "doesn't throw")
fc.assert(
  fc.property(fc.string(), (text) => {
    parse(text); // No assertion
  }),
);

TypeScript coverage commands (vitest):

Baseline (excluding test under audit):

pnpm vitest run --coverage --exclude='path/to/test-under-audit.test.ts'

With test:

pnpm vitest run --coverage 'path/to/test-under-audit.test.ts'

Alternative tooling: Projects may use c8, istanbul, or v8 coverage providers. Check vitest.config.ts for the coverage.provider setting and adapt commands accordingly.

Report actual deltas:

Baseline: src/config-parser.ts — 43.2%
With test: src/config-parser.ts — 67.8%
Delta: +24.6% — new coverage ✓

</typescript_supplements>

<concrete_examples>

Example 1: APPROVED

Auditing spx/21-config.enabler/43-parser.outcome/

Assertion mapping:

Assertion: MUST: Given a config file with nested sections, when parsed,
           then all section values are accessible by dotted path
Type: Scenario
Test: tests/config-parser.unit.test.ts ✓ exists

Coupling:

Import: import { parseConfig } from "../src/config-parser"
Classification: Direct — codebase import of module under test

Falsifiability:

Module: src/config-parser.ts
Mutation: parseConfig returns empty object instead of parsed sections
Impact: expect(result.section.key).toBe("value") fails — genuine falsifiability
No vi.mock or vi.spyOn found.

Alignment:

Assertion says: "nested sections → accessible by dotted path"
Test does: parseConfig(nestedInput) → asserts result.section.key
Match: exact behavior tested ✓
Assertion type: Scenario → example-based test strategy ✓

Coverage:

Baseline: src/config-parser.ts — 43.2%
With test: src/config-parser.ts — 67.8%
Delta: +24.6% ✓

Audit: spx/21-config.enabler/43-parser.outcome/
Verdict: APPROVED

| # | Assertion             | Coupling | Falsifiability             | Alignment | Coverage | Verdict |
|---|-----------------------|----------|----------------------------|-----------|----------|---------|
| 1 | Nested section access | Direct   | Empty object breaks assert | ✓         | +24.6%   | PASS    |

---

Example 2: REJECT — coupling severed by vi.mock

Auditing spx/32-api.enabler/54-auth.outcome/

Assertion: MUST: Given valid credentials, when authenticating,
           then a session token is returned from the database
Test: tests/auth.integration.test.ts ✓ exists

Coupling:

Import: import { database } from "../src/database"
Classification: Direct — but...
Line 8: vi.mock("../src/database", () => ({ query: vi.fn() }))
→ Coupling severed. Real database.query never runs.

Audit: spx/32-api.enabler/54-auth.outcome/
Verdict: REJECT

| # | Assertion     | Property Failed | Finding          | Detail                           |
|---|---------------|-----------------|------------------|----------------------------------|
| 1 | Session token | Falsifiability  | coupling severed | vi.mock replaces database module |

How tests could pass while assertions fail:
Database module is entirely replaced with a fake. Any schema change,
connection failure, or constraint violation in the real database is invisible.
The test verifies behavior against a vi.fn() that always succeeds.

---

Example 3: REJECT — type-only import disguised as coupling

Auditing spx/15-theme.enabler/22-contrast.outcome/

Assertion: MUST: All theme colors meet WCAG AA contrast ratio (4.5:1)
Test: tests/contrast.unit.test.ts ✓ exists

Coupling:

Imports:
  import { describe, expect, it } from "vitest"     → Framework
  import type { ThemeColor } from "../src/theme"     → Type-only (erased at runtime)

Zero runtime codebase imports → no coupling (tautology).

Audit: spx/15-theme.enabler/22-contrast.outcome/
Verdict: REJECT

| # | Assertion        | Property Failed | Finding     | Detail                                        |
|---|------------------|-----------------|-------------|-----------------------------------------------|
| 1 | WCAG AA contrast | Coupling        | no coupling | Only vitest + import type (erased at runtime) |

How tests could pass while assertions fail:
Test declares its own color constants and checks contrast math against them.
The actual theme colors in src/theme.ts are never read. If all theme colors
are changed to pure white, this test still passes.

</concrete_examples>

<failure_modes>

Failure 1: Accepted type-only import as coupling

Reviewer saw import type { ThemeColor } from "../src/theme" and classified it as direct coupling. But import type is erased at compile time — the test never touches the runtime module. The test declared its own OKLCH constants and verified contrast math with zero connection to any theme file.

How to avoid: Coupling supplement — import type does not count as a codebase import.

Failure 2: Missed coupling severed by vi.mock

Reviewer saw import { database } from "../src/database" and classified it as direct coupling. The next line was vi.mock("../src/database"). The real module never ran.

How to avoid: Falsifiability supplement — check for vi.mock/vi.spyOn after confirming coupling. Import + mock = coupling severed.

Failure 3: Confused barrel import with direct coupling

Test imported { validateConfig } from "../src/index". The assertion was about parseConfig. Both are exported from the same barrel, but the test never called parseConfig.

How to avoid: Coupling supplement — barrel re-exports can mask false coupling. Verify the specific export used matches the assertion.

Failure 4: Distracted by code quality while test was a tautology

Reviewer spent the entire audit checking for as any, verifying return types, and searching for skip patterns. The test had perfect TypeScript quality and zero evidentiary value — it imported only vitest.

How to avoid: Essential principles — no code quality checks. Check the four evidence properties only.

</failure_modes>

<rejection_triggers>

Category	Trigger	Property
Coupling	Zero codebase imports (only framework/library)	Coupling
Coupling	Only import type — erased at runtime	Coupling
Coupling	Barrel import of wrong export (false coupling)	Coupling
Coupling	Import present but assertion-relevant function never called	Coupling
Falsifiability	vi.mock / jest.mock replaces imported module	Falsifiability
Falsifiability	vi.spyOn / jest.spyOn with .mockReturnValue	Falsifiability
Falsifiability	Cannot name a concrete mutation that would fail the test	Falsifiability
Alignment	Parser/serializer without fc.assert roundtrip	Alignment
Alignment	Property assertion tested with only examples	Alignment
Alignment	Test exercises different behavior than assertion describes	Alignment
Coverage	Zero delta with baseline < 100% on assertion-relevant files	Coverage

</rejection_triggers>

<success_criteria>

Audit is complete when:

• /auditing-tests workflow executed (load context → map assertions → 4 properties → verdict)
• TypeScript supplements applied at each property step
• Coupling: imports classified (including import type, path aliases, barrel re-exports)
• Falsifiability: vi.mock/vi.spyOn patterns checked, exceptions identified
• Alignment: property-based testing verified for parsers/serializers/math/algorithms
• Coverage: actual deltas from vitest coverage command
• Verdict issued: APPROVED or REJECT
• For REJECT: each finding has property, finding category, detail
• For REJECT: "how tests could pass while assertions fail" explained

</success_criteria>