Running tests in Go - Step-by-Step Execution

Concept Flow - Running tests

Write test function

↓

Run 'go test'

↓

Test framework executes test

↓

Check test result

↓

Report success

This flow shows how Go runs tests: you write test functions, run 'go test', it executes tests, then reports pass or fail.

Execution Sample

Go

package main
import "testing"
func TestAdd(t *testing.T) {
  if 2+2 != 4 {
    t.Error("2+2 should be 4")
  }
}

This test checks if 2+2 equals 4 and reports an error if not.

Execution Table

Step	Action	Evaluation	Result
1	Run 'go test'	Find TestAdd function	TestAdd found
2	Execute TestAdd	Check if 2+2 == 4	True
3	No error called	Test passes	Pass
4	Report result	Output test summary	PASS

💡 TestAdd completes without error, so test passes and 'go test' reports success.

Variable Tracker

Variable	Start	After Step 2	Final
t.Error called	false	false	false
Test result	not run	running	pass

Key Moments - 2 Insights

Why does the test pass even though there is no explicit 'return true'?

In Go tests, if t.Error is not called, the test passes by default as shown in execution_table step 3.

What happens if the condition 2+2 != 4 is true?

If true, t.Error is called, marking the test as failed, which would be shown in execution_table step 3 as a failure.

Visual Quiz - 3 Questions

Look at the execution_table, what is the result after executing TestAdd?

A Pass

B Fail

C Error

D Skipped

💡 Hint

Check execution_table row 3 where the test result is 'Pass'.

At which step does the test framework find the test function?

A Step 3

B Step 1

C Step 2

D Step 4

💡 Hint

See execution_table row 1 where 'TestAdd found' is noted.

If the condition 2+2 != 4 was true, how would the variable 't.Error called' change?

A It would stay false

B It would be undefined

C It would become true

D It would reset to false

💡 Hint

Refer to variable_tracker and key_moments explaining t.Error call on failure.

Concept Snapshot

Go tests are functions starting with Test.
Run tests using 'go test' command.
If t.Error or t.Fail is called, test fails.
If no error, test passes by default.
Test results are reported after execution.

Full Transcript

In Go, you write test functions named starting with Test. When you run 'go test', the tool finds these functions and runs them. Inside a test, you check conditions. If a condition fails, you call t.Error to mark failure. If no errors occur, the test passes. The tool then reports the results. This example shows a test checking if 2+2 equals 4. Since it does, no error is called and the test passes.

Practice

1. What is the correct way to name a test function in Go so that go test can run it?

easy

A. Start the function name with Test

B. Start the function name with test (lowercase t)

C. Name the function RunTest

D. Name the function CheckTest

Solution

1. Step 1: Understand Go test naming rules

   Go requires test functions to start with an uppercase Test to be recognized by go test.

2. Step 2: Check the options

   Only Start the function name with Test starts with Test exactly, others do not follow the naming convention.

3. Final Answer:

   Start the function name with Test -> Option A

4. Quick Check:

   Test functions start with 'Test' [OK]

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

Common Mistakes:

• Using lowercase 'test' at start
• Naming test functions without 'Test' prefix
• Using unrelated prefixes like 'Run' or 'Check'

2. Which of the following is the correct syntax to run tests in a Go module from the command line?

easy

A. go execute test

B. go run test

C. go build test

D. go test

Solution

1. Step 1: Recall Go test command

   The command to run tests in Go is go test.

2. Step 2: Compare options

   Only go test matches the correct command. Others are invalid commands.

3. Final Answer:

   go test -> Option D

4. Quick Check:

   Run tests with 'go test' [OK]

Hint: Use 'go test' to run tests, not 'go run' [OK]

Common Mistakes:

• Using 'go run test' instead of 'go test'
• Trying 'go build test' which builds but doesn't test
• Using non-existent commands like 'go execute test'

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

package main

import "testing"

func TestSum(t *testing.T) {
  if 2+2 != 4 {
    t.Error("Sum failed")
  }
}

medium

A. Syntax error: missing main function

B. FAIL
--- FAIL: TestSum

C. PASS
ok main 0.001s

D. No tests to run

Solution

1. Step 1: Analyze the test logic

   The test checks if 2+2 equals 4, which is true, so no error is called.

2. Step 2: Understand test output

   Since the test passes, go test outputs PASS with timing info.

3. Final Answer:

   PASS ok main 0.001s -> Option C

4. Quick Check:

   Test passes, so output shows PASS [OK]

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

Common Mistakes:

• Assuming syntax error due to missing main
• Expecting FAIL when condition is true
• Thinking tests won't run without main function

4. Identify the error in this test function that prevents go test from running it:

package main

import "testing"

func testAdd(t *testing.T) {
  if 1+1 != 2 {
    t.Error("Add failed")
  }
}

medium

A. Missing import of 'fmt' package

B. Function name must start with uppercase 'Test'

C. Test function must return a value

D. Test functions cannot have parameters

Solution

1. Step 1: Check test function naming

   The function is named testAdd with lowercase 't', so go test ignores it.

2. Step 2: Verify other requirements

   Test functions must start with uppercase 'Test' and accept *testing.T parameter, which is correct except the name.

3. Final Answer:

   Function name must start with uppercase 'Test' -> Option B

4. Quick Check:

   Test functions need 'Test' prefix [OK]

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

Common Mistakes:

• Thinking test functions need to return a value
• Assuming missing 'fmt' import causes test failure
• Believing test functions cannot have parameters

5. You want to run only tests in the file math_test.go inside your module. Which command should you use?

hard

A. go test math_test.go

B. go test -file math_test.go

C. go test -v

D. go test -run math_test.go

Solution

1. Step 1: Understand how to run tests in a specific file

   Go allows specifying test files directly as arguments to go test.

2. Step 2: Check options for correct usage

   Only go test math_test.go runs tests in the specified file. B uses invalid -file flag, C's go test -v runs all tests verbosely, D's -run matches test names.

3. Final Answer:

   go test math_test.go -> Option A

4. Quick Check:

   Specify test file directly to run its tests [OK]

Hint: Run tests in a file by naming it after 'go test' [OK]

Common Mistakes:

• Using invalid flags like -run or -file with filenames
• Confusing verbose flag -v with file selection
• Not specifying the file and running all tests