Go Development Skill

You are a Go development specialist. This skill provides comprehensive guidance for Go development workflows, testing, and tooling.

Testing Workflow

STRONGLY PREFERRED: Use
gotestsum
for all test execution.

Running Tests with gotestsum

bash

# Basic test run (PREFERRED)
gotestsum ./...

# Short alias (if configured)
gt ./...

# Verbose output
gotestsum -v ./...

# Run specific test
gotestsum -run TestFunctionName ./...

# Run tests in a specific package
gotestsum ./pkg/mypackage/...

# Watch mode (rerun on file changes)
gotestsum --watch ./...

Test Output Formats

bash

# Default format (clean, colorized)
gotestsum ./...

# Show only test names
gotestsum --format testname ./...

# Dots format (. for pass, F for fail)
gotestsum --format dots ./...

# Group by package
gotestsum --format pkgname ./...

# Standard go test format (with colors)
gotestsum --format standard ./...

# TestDox format (BDD-style output)
gotestsum --format testdox ./...

Common Test Options

bash

# Run with race detection
gotestsum -race ./...

# Generate coverage
gotestsum -cover ./...
gotestsum -coverprofile=coverage.out ./...

# Verbose output
gotestsum -v ./...

# Short mode (skip long-running tests)
gotestsum -short ./...

# Fail fast (stop on first failure)
gotestsum --fail-fast ./...

# Run tests multiple times
gotestsum --count=10 ./...

# Parallel execution
gotestsum -p 4 ./...

# Timeout
gotestsum -timeout 30s ./...

Watch Mode for TDD

bash

# Watch and rerun tests on file changes
gotestsum --watch ./...

# Watch specific package
gotestsum --watch ./pkg/mypackage/...

# Watch with specific format
gotestsum --watch --format testdox ./...

Fallback to go test

gotestsum

is not available, use

go test

bash

# Basic test run
go test ./...

# Verbose
go test -v ./...

# With coverage
go test -cover ./...

Note: Always prefer

gotestsum

when available for better output formatting and colors.

Development Workflow

Standard Go Commands

bash

# Build the project
go build ./...

# Check compilation without building
go check ./...

# Run the application
go run ./cmd/myapp

# Install binary
go install ./cmd/myapp

# Format code
go fmt ./...
gofmt -w .

# Vet code for issues
go vet ./...

Module Management

bash

# Initialize module
go mod init github.com/user/project

# Add dependencies
go get github.com/some/package@v1.2.3

# Update dependencies
go get -u ./...

# Tidy dependencies (remove unused)
go mod tidy

# Vendor dependencies
go mod vendor

# Verify dependencies
go mod verify

# Download dependencies
go mod download

Building

bash

# Build current package
go build

# Build with output path
go build -o bin/myapp ./cmd/myapp

# Build all packages
go build ./...

# Cross-compile
GOOS=linux GOARCH=amd64 go build -o bin/myapp-linux ./cmd/myapp

# Build with version info
go build -ldflags "-X main.version=1.2.3" ./cmd/myapp

# Static binary (no CGO)
CGO_ENABLED=0 go build -o bin/myapp ./cmd/myapp

Code Quality

bash

# Format code
go fmt ./...

# Vet for issues
go vet ./...

# Run staticcheck (if installed)
staticcheck ./...

# Run golangci-lint (if installed)
golangci-lint run

# Check imports
goimports -w .

Testing Best Practices

Test File Organization

// mypackage_test.go
package mypackage_test  // External tests (test public API)

// Or
package mypackage       // Internal tests (test private functions)

Writing Tests

// Table-driven tests (PREFERRED)
func TestMyFunction(t *testing.T) {
    tests := []struct {
        name    string
        input   string
        want    string
        wantErr bool
    }{
        {
            name:  "valid input",
            input: "hello",
            want:  "HELLO",
        },
        {
            name:    "empty input",
            input:   "",
            wantErr: true,
        },
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got, err := MyFunction(tt.input)
            if (err != nil) != tt.wantErr {
                t.Errorf("MyFunction() error = %v, wantErr %v", err, tt.wantErr)
                return
            }
            if got != tt.want {
                t.Errorf("MyFunction() = %v, want %v", got, tt.want)
            }
        })
    }
}

Test Helpers

// Use t.Helper() to mark test helpers
func assertNoError(t *testing.T, err error) {
    t.Helper()
    if err != nil {
        t.Fatalf("unexpected error: %v", err)
    }
}

// Use t.Cleanup() for teardown
func TestWithCleanup(t *testing.T) {
    tmpDir := setupTempDir(t)
    t.Cleanup(func() {
        os.RemoveAll(tmpDir)
    })
    // test code
}

Benchmarks

bash

# Run benchmarks
gotestsum -bench=. ./...

# Or with go test
go test -bench=. ./...

# Benchmark with memory allocation stats
go test -bench=. -benchmem ./...

# Run specific benchmark
go test -bench=BenchmarkMyFunction ./...

Common Workflows

TDD Workflow

bash

# 1. Start watch mode
gotestsum --watch --format testdox ./...

# 2. Write failing test
# 3. Write code to make test pass
# 4. Refactor
# 5. Repeat

Pre-commit Checks

bash

# Format, vet, and test
go fmt ./... && go vet ./... && gotestsum ./...

# With race detection and coverage
go fmt ./... && go vet ./... && gotestsum -race -cover ./...

Coverage Analysis

bash

# Generate coverage report
gotestsum -coverprofile=coverage.out ./...

# View coverage in browser
go tool cover -html=coverage.out

# Show coverage per function
go tool cover -func=coverage.out

# Check coverage percentage
go tool cover -func=coverage.out | grep total

Debugging Tests

bash

# Run specific test with verbose output
gotestsum -v -run TestSpecificFunction ./...

# Run tests with print debugging
gotestsum -v ./... 2>&1 | grep "DEBUG"

# Use delve for debugging
dlv test ./pkg/mypackage -- -test.run TestSpecificFunction

Environment Variables

bash

# Disable CGO
export CGO_ENABLED=0

# Set GOOS/GOARCH for cross-compilation
export GOOS=linux
export GOARCH=amd64

# Set Go module proxy
export GOPROXY=https://proxy.golang.org,direct

# Private modules
export GOPRIVATE=github.com/myorg/*

# Module download mode
export GOMODCACHE=$HOME/go/pkg/mod

gotestsum Advanced Features

Custom Test Commands

bash

# Run tests with custom go test flags
gotestsum -- -tags integration ./...

# Run with build constraints
gotestsum -- -tags "integration e2e" ./...

# JSON output for parsing
gotestsum --jsonfile=test-results.json ./...

# JUnit XML output (for CI)
gotestsum --junitfile=junit.xml ./...

Rerun Failed Tests

bash

# Run tests and save failures
gotestsum --rerun-fails ./...

# Rerun only failed tests from previous run
gotestsum --rerun-fails=2 ./...

Post-run Commands

bash

# Run command after tests
gotestsum --post-run-command='notify-send "Tests done"' ./...

# Multiple commands
gotestsum --post-run-command='echo "Tests complete" && ./deploy.sh' ./...

Quick Reference

bash

# Test with gotestsum (PREFERRED)
gotestsum ./...
gt ./...                    # If alias configured

# Watch mode for TDD
gotestsum --watch ./...

# Race detection
gotestsum -race ./...

# Coverage
gotestsum -cover ./...

# Verbose output
gotestsum -v ./...

# Specific test
gotestsum -run TestName ./...

# Fail fast
gotestsum --fail-fast ./...

# Format code
go fmt ./...

# Vet code
go vet ./...

# Build
go build ./...

# Run
go run ./cmd/myapp

# Module tidy
go mod tidy

Best Practices

Use gotestsum for all testing - Better output, colors, and features
Write table-driven tests - More maintainable and comprehensive
Use t.Helper() for test utilities - Clearer test failure locations
Run tests with -race - Catch race conditions early
Check coverage - Aim for high test coverage
Use go fmt - Consistent code formatting
Run go vet - Catch common mistakes
Keep tests fast - Use -short flag for quick feedback loops
Use subtests with t.Run() - Better organization and parallel execution
Clean up with t.Cleanup() - Proper resource management

CI/CD Integration

bash

# Typical CI test command
gotestsum --format pkgname --junitfile junit.xml -- -race -cover -coverprofile=coverage.out ./...

# Generate coverage report
go tool cover -html=coverage.out -o coverage.html

# Check coverage threshold
go tool cover -func=coverage.out | awk '/total:/ {if ($3+0 < 80.0) exit 1}'

go

NPX Install

Tags

SKILL.md Content

Go Development Skill

Testing Workflow

Running Tests with gotestsum

Test Output Formats

Common Test Options

Watch Mode for TDD

Fallback to go test

Development Workflow

Standard Go Commands

Module Management

Building

Code Quality

Testing Best Practices

Test File Organization

Writing Tests

Test Helpers

Benchmarks

Common Workflows

TDD Workflow

Pre-commit Checks

Coverage Analysis

Debugging Tests

Environment Variables

gotestsum Advanced Features

Custom Test Commands

Rerun Failed Tests

Post-run Commands

Quick Reference

Best Practices

CI/CD Integration