Test-driven basics in Go - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Test-Driven Development (TDD)?

TDD is a way to write software where you first write a test that fails, then write code to make the test pass, and finally clean up the code. It helps catch mistakes early and guides design.

beginner

In Go, which package is commonly used for writing tests?

The testing package is used in Go to write tests. It provides tools to create test functions and check results.

beginner

What is the typical order of steps in TDD?

1. Write a failing test.
2. Write code to pass the test.
3. Refactor the code.
4. Repeat.

beginner

How do you name a test function in Go?

Test functions start with Test followed by a name, for example, TestAdd. They take a pointer to testing.T as a parameter.

beginner

Why is writing tests first helpful?

Writing tests first helps you think about what your code should do before writing it. It makes your code clearer and reduces bugs.

What is the first step in Test-Driven Development?

A Run the program

B Write the full program

C Refactor the code

D Write a failing test

In TDD, you start by writing a test that fails to define what the code should do.

Which Go package do you import to write tests?

A testing

B fmt

C os

D net/http

The testing package provides tools for writing tests in Go.

How should a test function be named in Go?

A testFunction

B FunctionTest

C TestFunction

D functionTest

Test functions in Go start with Test followed by a descriptive name, with uppercase T.

What do you do after making a failing test pass in TDD?

A Write more tests

B Refactor the code

C Delete the test

D Run the program without tests

After passing the test, you clean up or improve the code without changing its behavior.

Why is TDD useful?

A It helps catch bugs early

B It removes the need for comments

C It makes coding slower

D It avoids writing tests

TDD helps find mistakes early by writing tests first.

Explain the three main steps of Test-Driven Development.

Think about the cycle of writing tests and code.

Describe how to write a simple test function in Go using the testing package.

Remember the naming and parameter rules for Go tests.

Practice

1. What is the main purpose of writing tests in Go using the testing package?

easy

A. To make the program run faster

B. To add comments to the code

C. To check if the code works correctly by running test functions

D. To create user interfaces

Solution

1. Step 1: Understand the role of tests in Go

   Tests are written to verify that the code behaves as expected.

2. Step 2: Identify what the testing package does

   The testing package provides tools to write and run tests that check code correctness.

3. Final Answer:

   To check if the code works correctly by running test functions -> Option C

4. Quick Check:

   Tests check code correctness = B [OK]

Hint: Tests verify code correctness before running fully [OK]

Common Mistakes:

• Thinking tests improve speed
• Confusing tests with comments
• Assuming tests create UI

2. Which of the following is the correct way to start a test function in Go?

easy

A. func testMyFunc(t *testing.T) {}

B. func MyFuncTest(t *testing.T) {}

C. func TestingMyFunc(t *testing.T) {}

D. func TestMyFunc(t *testing.T) {}

Solution

1. Step 1: Recall Go test function naming rules

   Test functions must start with "Test" and take a *testing.T parameter.

2. Step 2: Match the correct function signature

   Only func TestMyFunc(t *testing.T) {} follows this rule exactly.

3. Final Answer:

   func TestMyFunc(t *testing.T) {} -> Option D

4. Quick Check:

   Test functions start with "Test" = C [OK]

Hint: Test functions must start with uppercase 'Test' [OK]

Common Mistakes:

• Starting function name with lowercase 'test'
• Adding extra words before 'Test'
• Using wrong parameter types

3. What will be the output when running go test on this test file?

package main

import "testing"

func Add(a, b int) int {
    return a + b
}

func TestAdd(t *testing.T) {
    if Add(2, 3) != 5 {
        t.Error("Expected 5")
    }
}

medium

A. No output

B. PASS

C. Compilation error

D. FAIL with error 'Expected 5'

Solution

1. Step 1: Analyze the Add function and test

   The Add function returns the sum of 2 and 3, which is 5.

2. Step 2: Check the test condition

   The test expects Add(2, 3) to be 5, which is true, so no error is called.

3. Final Answer:

   PASS -> Option B

4. Quick Check:

   Correct sum means test passes = D [OK]

Hint: If test condition matches, output is PASS [OK]

Common Mistakes:

• Assuming test fails when condition is true
• Thinking test prints 'Expected 5' on success
• Confusing test failure with compile error

4. Identify the error in this test code snippet:

package main

import "testing"

func TestMultiply(t *testing.T) {
    result := Multiply(2, 3)
    if result != 6 {
        t.Error("Expected 6")
    }
}

medium

A. Multiply function is not defined

B. Missing import for Multiply function

C. Test function name should be lowercase

D. t.Error should be t.Fail

Solution

1. Step 1: Check if Multiply function is defined

   The code snippet does not show any definition or import of Multiply function.

2. Step 2: Understand Go requires functions to be defined or imported

   Without definition or import, the code will not compile.

3. Final Answer:

   Multiply function is not defined -> Option A

4. Quick Check:

   Undefined function causes compile error = A [OK]

Hint: Undefined functions cause compile errors [OK]

Common Mistakes:

• Thinking test function names can be lowercase
• Confusing t.Error with t.Fail
• Assuming missing import causes runtime error

5. You want to write a test that fails if a function returns an empty string. Which test code snippet correctly implements this check?

hard

A. func TestEmpty(t *testing.T) {
if MyFunc() == "" {
t.Error("Result should not be empty")
}
}

B. func TestEmpty(t *testing.T) {
if MyFunc() != "" {
t.Error("Result should be empty")
}
}

C. func TestEmpty(t *testing.T) {
if MyFunc() == nil {
t.Error("Result should not be nil")
}
}

D. func TestEmpty(t *testing.T) {
if MyFunc() == 0 {
t.Error("Result should not be zero")
}
}

Solution

1. Step 1: Understand the test goal

   The test should fail if the function returns an empty string "".

2. Step 2: Check each option's condition

   func TestEmpty(t *testing.T) { if MyFunc() == "" { t.Error("Result should not be empty") } } fails when MyFunc() returns "", which matches the goal.

3. Final Answer:

   func TestEmpty(t *testing.T) { if MyFunc() == "" { t.Error("Result should not be empty") } } -> Option A

4. Quick Check:

   Fail on empty string = A [OK]

Hint: Fail test if function returns empty string "" [OK]

Common Mistakes:

• Checking for nil instead of empty string
• Checking for zero instead of string
• Reversing the condition logic