What testing tools, packages, and approaches are commonly used in Go, and how should they be applied in practice?

In Go, the standard testing package is most commonly used for testing, allowing you to write unit tests and integration tests.

Main tools and approaches:

• testing — the basic package for writing tests, benchmarks, and examples.
• go test — command to run tests.
• Table-driven tests — a convenient way to cover different scenarios with a single test.
• Mocking — libraries like gomock or testify/mock are used to simulate dependencies.
• testify — a set of utilities for convenient assertions (assert, require) and mocks.
• Code coverage — using go test -cover to measure how much of the code is covered by tests.

Practical applications:

• Write tests immediately during function development.
• Use table-driven tests to verify different input data.
• Mock external dependencies to keep tests isolated.
• Write benchmarks for performance-critical sections.
• Run integration tests with real services or their emulators.

Example of a table-driven test:

func TestSum(t *testing.T) {
    tests := []struct {
        name string
        a, b int
        want int
    }{
        {"positive", 2, 3, 5},
        {"zero", 0, 0, 0},
        {"negative", -1, -1, -2},
    }

    for _, tt := range tests {
        t.Run(tt.name, func(t *testing.T) {
            got := Sum(tt.a, tt.b)
            if got != tt.want {
                t.Errorf("Sum(%d, %d) = %d; want %d", tt.a, tt.b, got, tt.want)
            }
        })
    }
}