Testing package overview in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple test function

What is the output when running this Go test code?

Go

package main

import (
	"testing"
)

func TestSum(t *testing.T) {
	sum := 2 + 3
	if sum != 5 {
		t.Errorf("Expected 5 but got %d", sum)
	}
}

func main() {}

A No output because main() is empty

B Compilation error due to missing main function

C

FAIL
--- FAIL: TestSum (0.00s)
    main_test.go:7: Expected 5 but got 6

D

PASS
ok   	command-line-arguments	0.001s

💡 Hint

Tests pass silently unless there is an error.

The test checks if 2 + 3 equals 5, which is true, so the test passes and Go test reports PASS.

❓ Predict Output

intermediate

Behavior of t.Fatal in tests

What happens when t.Fatal is called inside a test function?

Go

package main

import (
	"testing"
)

func TestFailNow(t *testing.T) {
	t.Fatal("Fatal error occurred")
	// This line will not run
	t.Log("This will not print")
}

func main() {}

A Test fails immediately and logs the fatal message; subsequent lines are skipped.

B Test logs the fatal message but continues running the rest of the test.

C Test passes because t.Fatal only logs a message.

D Compilation error because t.Fatal cannot be called directly.

💡 Hint

t.Fatal stops the test immediately after logging.

t.Fatal logs the message and stops the test immediately, so lines after it do not run.

❓ Predict Output

advanced

Output of a benchmark function

What output does this benchmark produce when run with 'go test -bench=.'?

Go

package main

import (
	"testing"
)

func BenchmarkLoop(b *testing.B) {
	for i := 0; i < b.N; i++ {
		_ = i * i
	}
}

func main() {}

A

goos: linux
goarch: amd64
BenchmarkLoop-8    1000000000               1.23 ns/op
PASS

B

BenchmarkLoop-8    1000000000               1.23 ms/op
FAIL

C No output because main() is empty

D Compilation error due to missing testing import

💡 Hint

Benchmarks report number of iterations and time per operation.

The benchmark runs b.N times and reports ns/op; the test passes if no error occurs.

❓ Predict Output

advanced

Effect of t.Skip in a test

What is the output when t.Skip is called inside a test function?

Go

package main

import (
	"testing"
)

func TestSkipExample(t *testing.T) {
	t.Skip("Skipping this test")
	t.Error("This error will not be reported")
}

func main() {}

A

--- FAIL: TestSkipExample (0.00s)
    main_test.go:8: This error will not be reported
FAIL

B

--- SKIP: TestSkipExample (0.00s)
    main_test.go:7: Skipping this test
PASS

C Test runs normally and reports no skip or fail

D Compilation error due to t.Skip usage

💡 Hint

t.Skip stops the test and marks it as skipped.

t.Skip stops the test immediately and marks it as skipped; errors after it are ignored.

🧠 Conceptual

expert

Understanding parallel tests with t.Parallel

Which statement best describes the behavior of tests that call t.Parallel() in Go?

A Tests calling t.Parallel() run concurrently and immediately without waiting for any other tests.

B Tests calling t.Parallel() run sequentially after all non-parallel tests complete.

C Tests calling t.Parallel() run concurrently with other parallel tests but wait for the parent test to finish.

D Tests calling t.Parallel() cause the test suite to fail if run in parallel.

💡 Hint

Parallel tests run concurrently but respect the parent test's lifecycle.

t.Parallel marks the test to run concurrently with other parallel tests but waits for the parent test function to complete before finishing.