testvet

A Go static analysis tool that identifies missing test coverage and misplaced test functions in your Go projects.

Features

• Missing Test Detection: Finds functions and methods not called from any test function
• Low Coverage Detection: Identifies functions with statement coverage below a threshold (uses go test -cover)
• AST-Based Call Analysis: Analyzes actual function calls in tests, not naming conventions
• Misplaced Test Detection: Identifies tests that primarily call functions from a different source file
• Method Support: Handles methods with receivers, including generics
• Flexible Filtering: Option to exclude private (unexported) functions from analysis
• Clean Output: Organized results grouped by file with line numbers

Installation

go install github.com/LeanerCloud/testvet@latest

Or build from source:

git clone https://github.com/LeanerCloud/testvet.git
cd testvet
go build -o testvet .

Usage

# Analyze current directory (runs go test for coverage data by default)
testvet

# Analyze a specific directory
testvet -dir /path/to/your/project

# Exclude private (unexported) functions
testvet -dir . -exclude-private

# Show verbose output (parse warnings)
testvet -dir . -verbose

# Show functions with statement coverage below 80%
testvet -threshold 80

# Disable coverage filtering (AST-only analysis, faster but less accurate)
testvet -use-coverage=false

Example Output

================================================================================
GO TEST COVERAGE ANALYSIS
================================================================================
Project: /path/to/your/project

--------------------------------------------------------------------------------
FUNCTIONS WITHOUT TEST COVERAGE (3)
--------------------------------------------------------------------------------

handlers/user.go:
  Line 25: CreateUser
  Line 48: (UserService).ValidateEmail

utils/helpers.go:
  Line 12: parseConfig

--------------------------------------------------------------------------------
MISPLACED TESTS (1)
--------------------------------------------------------------------------------

TestCreateUser (line 15):
  Current file:  handlers/api_test.go
  Expected file: handlers/user_test.go

================================================================================
Summary: 3 functions without tests, 1 misplaced tests

With -threshold flag

When using -threshold, testvet also runs go test -cover and reports functions with statement coverage below the specified percentage:

--------------------------------------------------------------------------------
LOW COVERAGE FUNCTIONS (below 80.0%) (2)
--------------------------------------------------------------------------------

handlers/user.go:
  Line 25: CreateUser (45.5%)
  Line 48: ValidateEmail (72.0%)

================================================================================
Summary: 0 functions without tests, 0 misplaced tests, 2 low coverage functions

This helps identify functions that have tests but need more thorough testing (e.g., missing error path coverage).

How It Works

1. Parsing: Uses Go's go/ast package to parse all .go files in the target directory
2. Function Extraction: Extracts all function and method declarations from source files
3. Test Extraction: Identifies test functions (Test*, Benchmark*, Example*, Fuzz*) from _test.go files
4. Call Analysis: Walks the AST of each test function to find all function calls within it
5. Coverage Filtering (default): Runs go test -coverprofile and excludes functions with >=50% coverage from the "missing tests" list (catches indirectly tested functions)
6. Matching: A function is considered tested if it's called from any test function or has adequate coverage
7. Misplacement Detection: A test is misplaced if it primarily calls functions from a different source file

Excluded from Analysis

• main() and init() functions
• vendor/ directory
• testdata/ directory
• Hidden directories (starting with .)

Flags

Flag	Default	Description
-dir	.	Directory to analyze
-exclude-private	false	Exclude unexported functions from analysis
-verbose	false	Show verbose output including parse warnings
-threshold	0	Show functions with statement coverage below this percentage (0 to disable, excludes main/init)
-use-coverage	true	Use coverage data to filter out indirectly tested functions (functions with >=50% coverage are considered tested)

testvet vs go test -cover

These tools measure different aspects of test coverage:

Aspect	testvet	go test -cover
Question answered	Is this function called from any test?	What percentage of statements are executed?
Granularity	Per function (binary: yes/no)	Per statement (percentage)
Use case	Find completely untested functions	Measure thoroughness of existing tests

Example: A function with complex error handling might show:

• testvet: ✓ covered (called from a test)
• go test -cover: 60% (only the happy path is tested)

Both metrics are valuable:

• Use testvet to find functions with zero test coverage
• Use testvet -threshold N to find functions with low statement coverage
• Use go test -cover to measure overall statement coverage

# Find untested functions
testvet .

# Find functions with <80% statement coverage
testvet -threshold 80

# Measure overall statement coverage
go test -cover ./...

# View detailed coverage report
go test -coverprofile=coverage.out ./...
go tool cover -html=coverage.out

The -threshold flag bridges both approaches: it uses go test -cover under the hood but presents results in testvet's familiar format, making it easy to identify poorly-tested functions that need attention.

Limitations

• AST analysis only detects direct function calls within test functions (not calls from helper functions)

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

MIT License - see LICENSE for details.

Shameless plug

This tool is brought to you by LeanerCloud. We help companies reduce their cloud costs using a mix of services and tools such as AutoSpotting.

Running at significant scale on AWS and looking for cost optimization help? Contact us.