How to speed up tests by reusing context?

To speed up tests, you can reuse the context (for example, application, database, or environment context) instead of creating it anew for each test. This is especially useful for integration tests where initialization can be time-consuming.

Approaches:

• Use setup/teardown at the level of the entire test suite (for example, in TestMain in Go or beforeAll/afterAll in Jest) to create the context once.
• Cache connections to the database, external services, or mocks.
• Use a shared context with a timeout within tests, which is passed to functions.

Example in Go using TestMain:

var testCtx context.Context

func TestMain(m *testing.M) {
    testCtx = context.Background()
    // Initialize shared resources
    setupDatabase()
    code := m.Run()
    // Clean up resources
    teardownDatabase()
    os.Exit(code)
}

func TestSomething(t *testing.T) {
    // Use testCtx instead of creating a new one
    result := DoSomething(testCtx)
    if result != expected {
        t.Errorf("unexpected result")
    }
}

This approach reduces overhead for environment setup and speeds up test execution.