| name | test-smell-detection |
| description | Deep-dive audit using the full testsmells.org 19-smell academic catalog for tests in any language. Every finding maps to a named, citable smell from the research literature (Assertion Roulette, Duplicate Assert, Mystery Guest, Eager Test, Sensitive Equality, Conditional Test Logic, Sleepy Test, Magic Number Test, etc.) with research-backed severity. Polyglot: .NET (MSTest/xUnit/NUnit/TUnit), Python (pytest/unittest), TS/JS (Jest/Vitest/Mocha/node:test), Java (JUnit/TestNG), Go, Ruby (RSpec/Minitest), Rust, Swift, Kotlin (JUnit/Kotest), PowerShell (Pester), C++ (GoogleTest/Catch2). INVOKE ONLY when explicitly asked for the testsmells.org 19-smell academic catalog or citable smell names from the literature. DO NOT USE FOR: general or pragmatic audits — use test-anti-patterns; writing new tests (use code-testing-agent, or writing-mstest-tests for MSTest); running tests (use run-tests); framework migration.
|
| license | MIT |
Test Smell Detection
Deep formal audit of test code in any supported language using an academic test smell taxonomy. Detects symptoms of bad design or implementation decisions that make tests harder to understand, more fragile, less effective at catching bugs, or more expensive to maintain. Produces a severity-ranked report with specific locations and actionable fixes.
Language-specific guidance: Call the test-analysis-extensions skill to discover available extension files, then read the file matching the target codebase. The extension file documents test markers, sleep / time / random APIs, skip annotations, setup/teardown, mystery-guest indicators (file/database/network/env), integration markers, and language-specific calibration notes that drive the smell detectors below.
Why Test Smells Matter
Test smells erode confidence in a test suite and inflate maintenance costs:
| Problem | Consequence |
|---|
| Tests with conditional logic | Some paths never execute — hidden testing gaps |
| Tests that depend on external resources | Flaky failures, slow execution, environment coupling |
| Tests that sleep to wait for results | Non-deterministic timing, slow suites, false failures |
| Tests without assertions | False confidence — coverage looks good but nothing is verified |
| Tests that call many production methods | Hard to diagnose failures, unclear what's being tested |
| Tests with magic numbers | Unreadable intent, unclear boundary conditions |
| Tests relying on ToString for comparison | Brittle to formatting changes, obscure failure messages |
| Tests with exception handling logic | Swallowed failures, tests that pass when they shouldn't |
When to Use
- User asks for a comprehensive or formal test smell audit
- User asks "are my tests well-written?" and wants a thorough analysis
- User wants a test quality health check with academic rigor
- User asks for a review of test design or structure using standard smell categories
- User suspects tests are fragile, flaky, or giving false confidence and wants a deep investigation
When Not to Use
- User wants a quick pragmatic test review (use
test-anti-patterns — faster, covers the most common issues)
- User wants to evaluate assertion diversity specifically (use
assertion-quality)
- User wants to find duplicated boilerplate across tests (use
exp-test-maintainability)
- User wants to write new tests from scratch (help them directly)
- User wants to fix a specific failing test (diagnose and fix directly)
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, for context on whether patterns are justified |
Workflow
Step 1: Detect language and load extension
Identify the target codebase's language and test framework. Call the test-analysis-extensions skill and read the matching extension file (e.g., extensions/dotnet.md, extensions/python.md, extensions/typescript.md, extensions/go.md). The extension file lists the framework-specific test markers, sleep / wait APIs, skip / ignore attributes, mystery-guest indicators, and integration-test markers that the smell detectors below need.
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 loaded language extension file.
For a thorough audit, also consult the extended smell catalog which covers 9 additional smell types beyond the core 10 below.
Step 3: Scan for test smells
For each test method and class, check for the following smell categories. Examples reference .NET attributes but the patterns apply across all supported languages — use the loaded language extension file to map each pattern to the framework you are auditing.
Smell 1: Conditional Test Logic
Test methods containing if, else, switch, ternary (? :), for, foreach, while, or pattern-match arms that change assertion behavior. Control flow in tests means some paths may never execute, hiding gaps.
Severity: High
Detection: Any control-flow statement inside a test method body that affects which assertions run.
Exceptions (per-language idioms, do NOT flag):
- Foreach-assert used solely to assert every item in a known collection (the assertion is the loop body).
- Go / Rust table-driven tests:
for _, tt := range tests { t.Run(tt.name, func(t *testing.T) { ... }) } (Go) or #[rstest] parametrized loops are idiomatic.
it.each(...) / test.each(...) / @pytest.mark.parametrize / [Theory] + [InlineData] / @ParameterizedTest parametrization driven by data tables.- Pester
-ForEach / -TestCases and RSpec where blocks.
- Catch2
SECTIONs and GENERATE(...), doctest SUBCASE, GoogleTest INSTANTIATE_TEST_SUITE_P.
Smell 2: Mystery Guest
Tests that depend on external resources — files on disk, databases, network endpoints, environment variables — without making the dependency explicit or using test doubles.
Severity: High
Detection: Test methods that read files, open database connections, make HTTP requests (without a test handler), read environment variables, or use hard-coded file paths. Per language: File.ReadAllText / Directory.GetFiles / HttpClient / Environment.GetEnvironmentVariable (.NET); open() / pathlib.Path.read_text() / requests.get() / os.environ[...] (Python); fs.readFileSync / fetch(...) / process.env.X (JS/TS); Files.readAllBytes / Files.newInputStream / HttpClient.send / System.getenv (Java); os.ReadFile / http.Get / os.Getenv (Go); File.read / Net::HTTP.get / ENV[...] (Ruby); std::fs::read_to_string / reqwest::get / std::env::var (Rust); String(contentsOfFile:) / URLSession.shared.data / ProcessInfo.processInfo.environment (Swift); File(...).readText() / URL(...).openConnection() / System.getenv (Kotlin); Get-Content / Invoke-WebRequest / $env:X (Pester); std::ifstream / curl_easy_perform / std::getenv (C++).
Exception: In-memory fakes, test-specific handlers, or hermetic test data factories are fine.
Smell 3: Sleepy Test
Tests that call sleep or delay functions to wait for a condition. These introduce non-deterministic timing and slow down the suite.
Severity: High
Calibration: Severity does not drop because the test is an integration test — a fixed sleep is still flaky and slow there. Report it as High and recommend polling/awaiting the condition with a timeout.
Detection: Calls to sleep/delay functions inside test methods: Thread.Sleep / Task.Delay (.NET); time.sleep / asyncio.sleep (Python); setTimeout / await new Promise(r => setTimeout(...)) / jest.advanceTimersByTime not paired with a wait (JS/TS); Thread.sleep / TimeUnit.SECONDS.sleep (Java); time.Sleep (Go); sleep / Kernel#sleep (Ruby); std::thread::sleep / tokio::time::sleep (Rust); Thread.sleep / delay (Kotlin coroutines); sleep(_:) / Task.sleep (Swift); Start-Sleep (Pester); std::this_thread::sleep_for (C++). See the matching language extension file for the full list.
Smell 4: Assertion-Free Test (Unknown Test)
Tests that execute code but never assert anything. Test frameworks report these as passing even if the code is completely broken, as long as no exception is thrown.
Severity: High
Detection: A test method with no assertion calls and no expected-exception annotation. Framework-specific: missing Assert.* (.NET); no assert / pytest.raises (Python); no expect(...) or assert.* (JS/TS); no assert* / assertThat (Java); no t.Error* / t.Fatal* / assert.* testify (Go); no expect/.to/.eq (RSpec) or assert*/refute* (Minitest); no assert*! / assert_eq! / panic! (Rust); no XCTAssert* / #expect (Swift); no assert* / should* / Kotest matchers (Kotlin); no Should -* (Pester); no EXPECT_* / ASSERT_* / REQUIRE / CHECK (C++).
Calibration:
- A method named
*_DoesNotThrow / *_no_exception / should not throw is implicitly asserting no exception — still flag it but note it may be intentional.
- Mock-call verifications count as assertions:
mock.Verify(...) (Moq), Mock.AssertWasCalled (NSubstitute), mock.assert_called_with(...) (Python), expect(mock).toHaveBeenCalledWith(...) (Jest), verify(mock).method(...) (Mockito), Should -Invoke (Pester) — do NOT flag tests using these as assertion-free.
- Bare assertion forms count:
assert x == y (pytest), if got != want { t.Errorf(...) } (Go), assert!(cond) (Rust) are canonical.
- Snapshot assertions count:
.toMatchSnapshot() (Jest), syrupy (pytest), SnapshotTesting (Swift), approval-tests are real assertions.
- Missing await on async assertions is its own critical smell:
expect(promise).resolves.toBe(x) without await/return (Jest), un-awaited Assert.ThrowsAsync (xUnit), un-awaited coroutines in pytest-asyncio, Kotest tests without runTest, Swift Testing async cases without await. These tests have assertion calls but silently pass — flag with a dedicated note.
Smell 5: Eager Test
A test method that calls many different production methods, making it unclear what behavior is being tested. When it fails, diagnosis is difficult because the failure could stem from any of the calls.
Severity: Medium
Detection: A test method that calls 4+ distinct methods on the production object (excluding setup/construction). Count unique method names, not call count.
Calibration: Integration / end-to-end / workflow tests may legitimately call multiple methods. Check for integration markers in the loaded language extension file (e.g., [Trait("Category", "Integration")], @Tag("integration"), pytest.mark.integration, *_integration_test.go, Describe ... -Tag 'Integration') and downgrade.
Smell 6: Magic Number Test
Assertions that contain unexplained numeric literals. The intent of Assert.AreEqual(42, result) / assert result == 42 / expect(result).toBe(42) is unclear without context — what does 42 represent?
Severity: Medium
Detection: Numeric literals (other than 0, 1, -1, and the literal used in the test name) appearing as expected parameters in assertion methods or comparison operands.
Calibration: Small integers in context (like count checks Assert.AreEqual(3, list.Count) / assert len(items) == 3 / expect(arr.length).toBe(3) where 3 items were just added) are acceptable — only flag when the number's meaning is genuinely unclear.
Smell 7: Sensitive Equality
Tests that use string conversion for comparison or assertion. If the underlying string representation changes, the test breaks even though the actual behavior is correct.
Severity: Medium
Detection: Assert.AreEqual(expected, obj.ToString()) (.NET); assert str(obj) == "..." or assert repr(obj) == "..." (Python); expect(obj.toString()).toBe("...") or expect(${obj}).toBe(...) (JS/TS); assertEquals(expected, obj.toString()) (Java); assert.Equal(t, "...", fmt.Sprint(obj)) or obj.String() chains (Go); expect(obj.to_s).to eq("...") (RSpec); assert_eq!(format!("{}", obj), "...") or assert_eq!(format!("{:?}", obj), "...") (Rust); XCTAssertEqual(obj.description, "...") or string-interpolation assertion (Swift); assertEquals("...", obj.toString()) (Kotlin); Should -Be "..." against a [string]$obj (Pester); EXPECT_EQ("...", std::to_string(obj)) (C++).
Smell 8: Exception Handling in Tests
Tests that contain try/catch/except/rescue blocks or throw/raise/panic/return err statements used to manage exception flow instead of asserting on it. This typically means the test is manually managing errors rather than using the framework's built-in exception assertion facilities.
Severity: Medium
Detection: try/catch (.NET, Java, JS/TS, Kotlin, Swift, C++); try/except (Python); begin/rescue (Ruby); defer recover() (Go); manual if err != nil { t.Fatal(err) } in Go is canonical and NOT a smell.
Exception: catch/except/rescue blocks that capture an exception for further assertion on its properties are a lesser concern — note but don't flag as high severity.
Smell 9: General Fixture (Over-broad Setup)
The test setup method, constructor, or fixture initializes fields that are not used by every test method. This means each test pays the cost of setting up objects it doesn't need.
Severity: Low
Detection: Fields/properties initialized in [TestInitialize] / setUp / @BeforeEach / beforeEach / before(:each) / BeforeEach (Pester) / setUpWithError (XCTest) / pytest fixture(autouse=True) / xUnit constructor / Kotest beforeTest that are referenced by fewer than half the test methods in the class/module/file.
Smell 10: Ignored / Disabled / Skipped Test
Tests marked as skipped or disabled. These add overhead and clutter, and the underlying issue they were disabled for may never be addressed.
Severity: Low
Detection: Skip / ignore / disable annotations or conditional compilation that disables a test. See the loaded language extension file for framework-specific skip attributes — e.g., [Ignore] (MSTest/NUnit), Skip = "..." (xUnit Fact), @Ignore (TUnit/JUnit 4), @Disabled (JUnit 5), @pytest.mark.skip / pytest.skip(...) / pytestmark, it.skip / xit / describe.skip / test.skip (Jest/Vitest/Mocha), t.Skip(...) (Go), pending / skip / xit (RSpec), #[ignore] (Rust), XCTSkip / @Test(.disabled) (Swift), @Ignored (Kotest), -Skip (Pester), GTEST_SKIP() / DISABLED_TestName (GoogleTest), [.] tag (Catch2), TEST_CASE("...", "[.]") skip.
Step 4: Apply calibration rules
Before reporting, calibrate findings to avoid false positives:
- Integration tests have different norms — but not for sleeps. A test class clearly marked as integration (by name, annotation, category, or convention — see the loaded language extension file for markers) legitimately uses external resources and calls multiple methods. Downgrade Mystery Guest and Eager Test for integration tests. Do NOT downgrade Sleepy Test: a fixed wall-clock sleep is non-deterministic and slow in any test category, so it stays a real High-severity smell — recommend polling/awaiting the condition with a timeout instead. Only treat a sleep as acceptable when it is bounded by a documented external constraint (e.g. a third-party rate limit) and paired with a condition check.
- Simple loop-assert patterns are fine. Iterating a collection to assert on every item is readable and correct. Only flag loops with complex branching logic.
- Idiomatic table-driven and parametrized patterns are NOT Conditional Test Logic. Go's
for _, tt := range tests { t.Run(...) }, Rust's #[rstest], pytest's @parametrize, Jest/Vitest .each, JUnit @ParameterizedTest, RSpec where, Pester -ForEach, Catch2 SECTION/GENERATE, GoogleTest INSTANTIATE_TEST_SUITE_P are canonical and must NOT be flagged.
- Context matters for magic numbers. A count assertion right after adding a known number of items is self-documenting. Only flag numbers whose meaning requires looking at production code to understand.
- Bare
assert (pytest) is canonical, not assertion-free framework use. Don't flag.
- Go's
if err != nil { t.Fatal(err) } is canonical, not Exception Handling in Tests. Don't flag.
- Mock-call verifications and snapshot assertions are real assertions — do not flag tests using them as Assertion-Free.
- Missing-await on async assertions is its own critical sub-smell of Assertion-Free — these tests silently pass even when the underlying assertion fails. Always flag when detected.
- Inconclusive/pending markers are not assertion-free. Tests explicitly marked as incomplete should be flagged as Ignored Test, not Assertion-Free.
- Capture-and-assert exception patterns are borderline.
try { ... } catch (X x) { Assert.Equal(...) } style patterns are ugly but functional. Note as a smell and suggest the framework's built-in exception assertion (, , , , , etc.) instead of calling it broken.
Step 5: Report findings
Present the analysis in this structure:
-
Summary Dashboard — Quick overview:
| Severity | Smell Count | Affected Tests |
|----------|-------------|----------------|
| High | 3 | 7 |
| Medium | 2 | 4 |
| Low | 1 | 2 |
| Total | 6 | 13 |
-
Findings by Severity — For each smell found:
- Smell name and category
- Severity level with rationale
- Affected test methods (file and method name)
- Code snippet showing the smell
- Concrete fix: show what the code should look like after remediation
- Risk if left unfixed
-
Smell-Free Patterns — If any test methods are well-written, briefly acknowledge this. Highlighting what's good helps the user understand the contrast.
-
Prioritized Remediation Plan — Rank fixes by:
- Impact (high-severity smells affecting many tests first)
- Effort (quick fixes before refactoring)
- Risk (fixes that prevent false-passes before cosmetic improvements)
Validation
Common Pitfalls
| Pitfall | Solution |
|---|
| Flagging integration tests for using real resources | Check for integration test markers (per the loaded language extension) and adjust severity accordingly — external resources and multi-step flows are expected there |
| Calibrating away a real sleep as an "integration style issue" | Thread.Sleep(3000) in an integration test is still a High-severity Sleepy Test; recommend a polled wait with timeout |
| Flagging loop-over-collection-assert as conditional logic | Only flag loops with branching or complex logic, not assertion iterations |
| Flagging Go/Rust table-driven loops as Conditional Test Logic | for _, tt := range tests { t.Run(...) } (Go) and #[rstest] loops (Rust) are canonical and must NOT be flagged |
| Flagging parametrized tests as Duplicate Assert | @pytest.mark.parametrize, it.each, [Theory]+[InlineData], @ParameterizedTest, RSpec where, Pester -ForEach, Catch2 SECTION/GENERATE are correct deduplication, not smells |
| Flagging obvious count assertions after adding N items | Consider the immediate context — self-documenting numbers are fine |
| Missing framework-specific assertion syntax | Always read the matching language extension file first; each framework has distinct assertion APIs (xUnit Assert.Equal, MSTest Assert.AreEqual, NUnit Is.EqualTo, pytest bare assert, Jest expect().toBe(), etc.) |
| Treating mock-call verifications as assertion-free | mock.Verify(...), expect(mock).toHaveBeenCalledWith(...), Should -Invoke, verify(mock).method(...), mock.assert_called_with(...) are real assertions |
| Missing the async-test silent-pass trap | Always flag expect(promise).resolves.toBe(x) without await/return, un-awaited Assert.ThrowsAsync (xUnit), un-awaited coroutines in pytest-asyncio, missing runTest in Kotest, un-awaited Swift Testing async assertions |
