How to Write Integration Tests in Go

Write integration tests in Go by creating a _test.go file in your package, importing testing, and defining functions starting with Test that exercise your code's interaction with external systems or complex setups.

package mypkg

import (
	"os"
	"testing"
)

func TestIntegrationExample(t *testing.T) {
	// Setup: Create a temporary file for the test
	tmpFile, err := os.CreateTemp("", "test-*.txt")
	if err != nil {
		t.Fatal(err)
	}
	defer os.Remove(tmpFile.Name())

	// Exercise: Write data and read it back
	_, err = tmpFile.WriteString("hello")
	if err != nil {
		t.Fatal(err)
	}
	tmpFile.Close()

	data, err := os.ReadFile(tmpFile.Name())
	if err != nil {
		t.Fatal(err)
	}

	// Verify: Check the result
	if string(data) != "hello" {
		t.Errorf("expected 'hello', got %q", string(data))
	}
}

Integration tests check if different parts of your software work together correctly, like verifying a database connection or file writing. Unlike unit tests that check one small function in isolation, these tests run the whole flow to ensure everything connects properly. Think of it as a rehearsal for the entire play rather than just checking if one actor knows their lines.