Running tests in Go - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Go test function?

Consider the following Go test code. What will be printed when running go test?

Go

package main

import (
	"testing"
)

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

A

FAIL
Expected 5 but got 5

B

TestSum completed
PASS

C No output

D

PASS
TestSum completed

💡 Hint

Remember that println outputs to standard output and test failures print error messages.

The test passes because sum equals 5, so no error is printed. The println statement outputs 'TestSum completed' before the test finishes, then 'PASS' is printed by the test runner.

❓ Predict Output

intermediate

What error does this Go test produce?

What error message will this Go test produce when run?

Go

package main

import "testing"

func TestFail(t *testing.T) {
	if 1+1 != 3 {
		t.Fatal("Math is broken")
	}
}

A

Math is broken
FAIL

B PASS

C panic: Math is broken

D No output

💡 Hint

t.Fatal stops the test immediately and prints the message.

The condition is true, so t.Fatal prints 'Math is broken' and marks the test as failed.

🔧 Debug

advanced

Why does this Go test not run any tests?

Given this Go test file, why does running go test report 'no tests to run'?

Go

package main

import "testing"

func sum(t *testing.T) {
	if 2+2 != 4 {
		t.Error("Wrong sum")
	}
}

A Test functions cannot take parameters

B Test function must return an error

C Function name must start with 'Test' to be recognized as a test

D Missing import of 'fmt' package

💡 Hint

Test functions must follow a naming convention to be detected.

Go test looks for functions starting with 'Test' and taking *testing.T as parameter. 'sum' does not start with 'Test', so it is ignored.

📝 Syntax

advanced

What syntax error does this Go test code produce?

Identify the syntax error in this Go test code snippet.

Go

package main

import "testing"

func TestExample(t *testing.T) {
	if 1 == 1 {
		t.Log("One equals one")
	} else
		t.Error("Math error")
}

A No syntax error, code runs fine

B Syntax error: missing parentheses around else condition

C Syntax error: missing semicolon after t.Log call

D Syntax error: else must be on the same line as closing brace

💡 Hint

In Go, else must be on the same line as the closing brace of if block.

Go requires the else keyword to be on the same line as the closing brace of the if block. Here, else is on the next line, causing a syntax error.

🚀 Application

expert

How many tests are run by this Go test file?

Given this Go test file, how many tests will go test run?

Go

package main

import "testing"

func TestOne(t *testing.T) {}

func TestTwo(t *testing.T) {}

func testThree(t *testing.T) {}

func TestFour() {}

func TestFive(t *testing.T) {
	t.Run("Subtest", func(t *testing.T) {})
}

A 3

B 4

C 5

D 2

💡 Hint

Only functions starting with 'Test' and taking *testing.T run as tests. Subtests count as part of parent test.

TestOne, TestTwo, and TestFive are valid tests. testThree is lowercase, TestFour lacks parameter, so only 3 tests run. Subtest inside TestFive is not counted separately.