Test Anti-Pattern Detection

Quick, pragmatic analysis of .NET test code for anti-patterns and quality issues that undermine test reliability, maintainability, and diagnostic value.

When to Use

• User asks to review test quality or find test smells

• User wants to know why tests are flaky or unreliable

• User asks "are my tests good?" or "what's wrong with my tests?"

• User requests a test audit or test code review

• User wants to improve existing test code

When Not to Use

• User wants to write new tests from scratch (use writing-mstest-tests)

• User wants direct implementation fixes in MSTest code rather than a diagnostic review (use writing-mstest-tests)

• User asks to fix swapped Assert.AreEqual argument order (use writing-mstest-tests)

• User asks to convert DynamicData from IEnumerable<object[]> to ValueTuple (use writing-mstest-tests)

• User wants to run or execute tests (use run-tests)

• User wants to migrate between test frameworks or versions (use migration skills)

• User wants to measure code coverage (out of scope)

• User wants a deep formal test smell audit with academic taxonomy and extended catalog (use test-smell-detection)

Inputs

Input

Required

Description

Test code

Yes

One or more test files or classes to analyze

Production code

No

The code under test, for context on what tests should verify

Specific concern

No

A focused area like "flakiness" or "naming" to narrow the review

Workflow

Step 1: Gather the test code

Read the test files the user wants reviewed. If the user points to a directory or project, scan for all test files using the framework-specific markers in the dotnet-test-frameworks skill (e.g., [TestClass], [Fact], [Test]).

If production code is available, read it too -- this is critical for detecting tests that are coupled to implementation details rather than behavior.

Step 2: Scan for anti-patterns

Check each test file against the anti-pattern catalog below. Report findings grouped by severity.

#### Critical -- Tests that give false confidence

Anti-Pattern

What to Look For

No assertions

Test methods that execute code but never assert anything. A passing test without assertions proves nothing.

Coverage touching

Test class that methodically calls every public method on a type — often in alphabetical or declaration order — without asserting meaningful outcomes. Each test typically does var result = sut.MethodName(...) with no assertion, or only a trivial Assert.IsNotNull(result). The intent is to inflate code-coverage metrics rather than verify behavior. Distinct from a single assertion-free test: the pattern is systematic coverage of the surface area with no real verification.

Self-referential assertion

Asserts that the output of an operation equals its input when the operation is expected to be an identity or no-op, e.g. Assert.AreEqual(input, Parse(input.ToString())) or Assert.AreEqual(x, Identity(x)). The test is tautological — it can only fail if the round-trip is broken, but it never verifies that a transformation actually happened. Also catches Assert.AreEqual(dto.Name, dto.Name) (asserting a field against itself).

Swallowed exceptions

try { ... } catch { } or catch (Exception) without rethrowing or asserting. Failures are silently hidden.

Assert in catch block only

try { Act(); } catch (Exception ex) { Assert.Fail(ex.Message); } -- use Assert.ThrowsException or equivalent instead. The test passes when no exception is thrown even if the result is wrong.

Always-true assertions

Assert.IsTrue(true), Assert.AreEqual(x, x), or conditions that can never fail.

Commented-out assertions

Assertions that were disabled but the test still runs, giving the illusion of coverage.

#### High -- Tests likely to cause pain

Anti-Pattern

What to Look For

Flakiness indicators

Thread.Sleep(...), Task.Delay(...) for synchronization, DateTime.Now/DateTime.UtcNow without abstraction, Random without a seed, environment-dependent paths.

Test ordering dependency

Static mutable fields modified across tests, [TestInitialize] that doesn't fully reset state, tests that fail when run individually but pass in suite (or vice versa).

Over-mocking

More mock setup lines than actual test logic. Verifying exact call sequences on mocks rather than outcomes. Mocking types the test owns. For a deep mock audit, use exp-mock-usage-analysis.

Implementation coupling

Testing private methods via reflection, asserting on internal state, verifying exact method call counts on collaborators instead of observable behavior.

Broad exception assertions

Assert.ThrowsException<Exception>(...) instead of the specific exception type. Also: [ExpectedException(typeof(Exception))].

#### Medium -- Maintainability and clarity issues

Anti-Pattern

What to Look For

Poor naming

Test names like Test1, TestMethod, names that don't describe the scenario or expected outcome. Good: Add_NegativeNumber_ThrowsArgumentException.

Magic values

Unexplained numbers or strings in arrange/assert: Assert.AreEqual(42, result) -- what does 42 mean?

Duplicate tests

Three or more test methods with near-identical bodies that differ only in a single input value. Should be data-driven ([DataRow], [Theory], [TestCase]). For a detailed duplication analysis, use exp-test-maintainability. Note: Two tests covering distinct boundary conditions (e.g., zero vs. negative) are NOT duplicates -- separate tests for different edge cases provide clearer failure diagnostics and are a valid practice.

Giant tests

Test methods exceeding ~30 lines or testing multiple behaviors at once. Hard to diagnose when they fail.

Assertion messages that repeat the assertion

Assert.AreEqual(expected, actual, "Expected and actual are not equal") adds no information. Messages should describe the business meaning.

Missing AAA separation

Arrange, Act, Assert phases are interleaved or indistinguishable.

#### Low -- Style and hygiene

Anti-Pattern

What to Look For

Unused test infrastructure

[TestInitialize]/[SetUp] that does nothing, test helper methods that are never called.

IDisposable not disposed

Test creates HttpClient, Stream, or other disposable objects without using or cleanup.

Console.WriteLine debugging

Leftover Console.WriteLine or Debug.WriteLine statements used during test development.

Inconsistent naming convention

Mix of naming styles in the same test class (e.g., some use Method_Scenario_Expected, others use ShouldDoSomething).

Step 3: Calibrate severity honestly

Before reporting, re-check each finding against these severity rules:

• Critical/High: Only for issues that cause tests to give false confidence or be unreliable. A test that always passes regardless of correctness is Critical. Flaky shared state is High.

• Medium: Only for issues that actively harm maintainability -- 5+ nearly-identical tests, truly meaningless names like Test1.

• Low: Cosmetic naming mismatches, minor style preferences, assertion messages that could be better. When in doubt, rate Low.

• Not an issue: Separate tests for distinct boundary conditions (zero vs. negative vs. null). Explicit per-test setup instead of [TestInitialize] (this improves isolation). Tests that are short and clear but could theoretically be consolidated.

IMPORTANT: If the tests are well-written, say so clearly up front. Do not inflate severity to justify the review. A review that finds zero Critical/High issues and only minor Low suggestions is a valid and valuable outcome. Lead with what the tests do well.

Step 4: Report findings

Present findings in this structure:

• Summary -- Total issues found, broken down by severity (Critical / High / Medium / Low). If tests are well-written, lead with that assessment.

• Critical and High findings -- List each with:

• The anti-pattern name

• The specific location (file, method name, line)

• A brief explanation of why it's a problem

• A concrete fix (show before/after code when helpful)

• Medium and Low findings -- Summarize in a table unless the user wants full detail

• Positive observations -- Call out things the tests do well (sealed class, specific exception types, data-driven tests, clear AAA structure, proper use of fakes, good naming). Don't only report negatives.

Step 5: Prioritize recommendations

If there are many findings, recommend which to fix first:

• Critical -- Fix immediately, these tests may be giving false confidence

• High -- Fix soon, these cause flakiness or maintenance burden

• Medium/Low -- Fix opportunistically during related edits

Validation

• Every finding includes a specific location (not just a general warning)

• Every Critical/High finding includes a concrete fix

• Report covers all categories (assertions, isolation, naming, structure)

• Positive observations are included alongside problems

• Recommendations are prioritized by severity

Common Pitfalls

Pitfall

Solution

Reporting style issues as critical

Naming and formatting are Medium/Low, never Critical

Suggesting rewrites instead of targeted fixes

Show minimal diffs -- change the assertion, not the whole test

Flagging intentional design choices

If Thread.Sleep is in an integration test testing actual timing, that's not an anti-pattern. Consider context.

Inventing false positives on clean code

If tests follow best practices, say so. A review finding "0 Critical, 0 High, 1 Low" is perfectly valid. Don't inflate findings to justify the review.

Flagging separate boundary tests as duplicates

Two tests for zero and negative inputs test different edge cases. Only flag as duplicates when 3+ tests have truly identical bodies differing by a single value.

Rating cosmetic issues as Medium

Naming mismatches (e.g., method name says ArgumentException but asserts ArgumentOutOfRangeException) are Low, not Medium -- the test still works correctly.

Ignoring the test framework

xUnit uses [Fact]/[Theory], NUnit uses [Test]/[TestCase], MSTest uses [TestMethod]/[DataRow] -- use correct terminology

Missing the forest for the trees

If 80% of tests have no assertions, lead with that systemic issue rather than listing every instance