Assertion QualitySAFE

Repository for skills to assist AI coding agents with .NET and C#

The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: assertion-quality
description: "Analyze assertion quality, depth, variety, and false confidence in existing tests. ALWAYS USE when asked about weak, shallow, trivial, always-true, self-referential, assertion-free, presence/truthiness-only, or insufficiently diverse assertions, including MSTest, Jest, pytest, and Go. DO NOT USE for direct fixes: writing-mstest-tests owns supplied MSTest assertions; code-testing owns new cases. Use test-gap-analysis when asked whether tests would catch a production change, and test-anti-patterns for general severity-ranked audits."
license: MIT
---

# Assertion Diversity Analysis

Analyze test code in any supported language to measure how varied and meaningful the assertions are. Produce a metrics report that reveals whether tests verify different facets of correctness — not just "output equals X" but also structure, exceptions, state transitions, side effects, and invariants.

> **Language-specific guidance**: Read the caller-provided or runtime-listed
> `test-analysis-extensions` catalog, then its matching language file
> (`dotnet.md`, `python.md`, `typescript.md`, `go.md`, etc.).
> `test-analysis-extensions` is reference-only; do not invoke it as a skill.
> If the bundle is absent, use the pinned framework and this skill's rules,
> report the missing reference, and do not search installation directories.

## Why Assertion Diversity Matters

Low assertion diversity signals shallow testing. Tests may pass while bugs hide in unasserted logic. Common symptoms:

| Problem | Symptom | Consequence |
|---------|---------|-------------|
| Trivial assertions | Test contains only `Assert.IsNotNull(result)` / `assert result is not None` / `expect(x).toBeDefined()` | Test passes but doesn't verify correctness |
| Single-value obsession | Always check one field or return value | Bugs in unasserted logic slip through |
| No negative assertions | Never check what shouldn't happen | Regressions sneak in through false positives |
| No state checks | Don't verify object state changes | Missed side-effects or lifecycle issues |
| No structural checks | Only assert top-level value | Bugs in nested objects go unnoticed |
| Assertion-free tests | Tests that call but don't verify | Code coverage lies; false security |

## When to Use

- User asks to evaluate assertion quality or depth
- User asks "are my tests actually testing anything meaningful?"
- User wants to know if test assertions are too shallow or trivial
- User asks for assertion coverage metrics or diversity analysis
- User suspects tests give false confidence despite passing
- The `test-engineer` agent (or any test-generation workflow) calls this skill as a pre-completion self-review step on freshly generated tests, before declaring the run finished

## When Not to Use

- User wants to write new tests (use `code-testing` for any language, or `writing-mstest-tests` for MSTest specifically)
- User wants to detect anti-patterns beyond assertions (use `test-anti-patterns`)
- User wants to fix or rewrite assertions (help them directly)
- User asks about code coverage percentages (out of scope — this analyzes assertion quality, not line coverage)

## Inputs

| Input | Required | Description |
|-------|----------|-------------|
| Test code | Yes | One or more test files or a test project directory to analyze |
| Production code | No | The code under test, to evaluate whether assertions cover the important behaviors |

## Workflow

### Step 1: Detect language and load extension

Identify the language and test framework. Read the corresponding file in
`extensions/` relative to the supplied `test-analysis-extensions` catalog.
Use that catalog for other language filenames. Check only that known
directory when necessary; an unavailable reference changes the evidence limit,
not the workspace root or the requested review.

### Step 2: Gather the test code

Read all test files the user provides. If the user points to a directory or project, scan for all test files using the markers in the language extension file (e.g., `[TestMethod]` for MSTest, `def test_*` for pytest, `it()` / `test()` for Jest, `func TestXxx` for Go).

### Step 3: Classify every assertion

For each test method, identify all assertions and classify them into these language-neutral categories:

| Category | What it verifies | Examples across languages |
|----------|------------------|----------------------------|
| **Equality** | Return value matches expected | `Assert.AreEqual` (MSTest), `Assert.Equal` (xUnit), `assert x == y` (pytest), `expect(x).toBe(y)` (Jest), `assertEquals` (JUnit), `if got != want { t.Error... }` / `assert.Equal(t, want, got)` (Go), `x shouldBe y` (Kotest), `Should -Be` (Pester), `EXPECT_EQ` (GoogleTest) |
| **Boolean** | Condition holds | `Assert.IsTrue`, `assert flag` (Python), `expect(x).toBeTruthy()` (Jest), `assertTrue` (JUnit), `assert.True(t, ok)` (testify), `x.shouldBeTrue()` (Kotest), `Should -BeTrue` (Pester), `EXPECT_TRUE` |
| **Null / None / Nil** | Presence/absence of value | `Assert.IsNull` (.NET), `assert x is None` (pytest), `expect(x).toBeNull()` (Jest), `assertNull` (JUnit), `assert.Nil(t, v)` (testify), `XCTAssertNil` (XCTest), `Should -BeNullOrEmpty` (Pester) |
| **Exception / Error** | Error handling behavior | `Assert.Throws<T>()`, `pytest.raises(E)`, `expect(fn).toThrow(E)`, `assertThrows<E>`, `assert.Error(t, err)` / `assert.ErrorIs`, `#[should_panic]` (Rust), `XCTAssertThrowsError`, `Should -Throw`, `EXPECT_THROW` |
| **Type checks** | Runtime type correctness | `Assert.IsInstanceOfType`, `assert isinstance(x, T)`, `expect(x).toBeInstanceOf(T)`, `assertInstanceOf`, `assert.IsType(t, T{}, v)`, `assert!(matches!(value, Pattern))` (Rust), `Should -BeOfType` |
| **String** | Text content and format | `StringAssert.Contains`, `assert sub in s`, `expect(s).toMatch(/x/)`, `assertTrue(s.contains(...))`, `assert.Contains(t, s, sub)`, `s shouldContain sub`, `Should -Match`, `EXPECT_THAT(s, HasSubstr(...))` |
| **C

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (0)

No findings outside the package's declared scope.

Gates applied: no_behavioural_pass.

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