How Can I Effectively Test for Panics in Go Unit Tests?

Testing Panics in Go: A Practical Guide

When writing unit tests in Go, it's often necessary to verify that a specific code path triggers a panic. While Go provides a mechanism called recover to handle panics, it doesn't offer direct support for specifying how to skip or execute code specifically in the event of a panic.

To overcome this limitation, we can utilize the subtlety that testing does not define the concept of success, but only failure. By taking advantage of this, we can structure our tests as follows:

func TestPanic(t *testing.T) {
    defer func() {
        if r := recover(); r == nil {
            t.Errorf("The code did not panic")
        }
    }()

    // The following is the code under test
    OtherFunctionThatPanics()
}

In this example, if OtherFunctionThatPanics doesn't panic, the recover function will return nil, and the test will fail due to the call to t.Errorf. If a panic does occur, recover will capture it, and the test will pass.

Alternatively, we can create a helper function to abstract away the panic-checking logic:

func assertPanic(t *testing.T, f func()) {
    defer func() {
        if r := recover(); r == nil {
            t.Errorf("The code did not panic")
        }
    }()
    f()
}

func TestPanic(t *testing.T) {
    assertPanic(t, OtherFunctionThatPanics)
}

This approach provides a concise and reusable way to handle panic testing in Go.

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