Writing basic test functions in Go - Step-by-Step Execution

Concept Flow - Writing basic test functions

Write test function with prefix Test

↓

Use *testing.T parameter

↓

Call function to test

↓

Check result with if condition

↓

Call t.Error or t.Fail if test fails

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Run tests with 'go test'

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See pass/fail output

This flow shows how to write a test function in Go, check results, and report failures using the testing package.

Execution Sample

Go

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

A simple test function that checks if Add(2, 3) returns 5 and reports an error if not.

Execution Table

Step	Action	Evaluation	Result
1	Call TestAdd with *testing.T	N/A	Test function starts
2	Call Add(2, 3)	Add returns 5	result = 5
3	Check if result != 5	5 != 5 is false	No error reported
4	Test function ends	N/A	Test passes

💡 Test ends after checking condition; no error means test passes

Variable Tracker

Variable	Start	After Step 2	Final
result	undefined	5	5

Key Moments - 3 Insights

Why must the test function name start with 'Test'?

Go's test runner looks for functions starting with 'Test' to know which functions to run as tests, as shown in step 1 of the execution_table.

What happens if the condition in the if statement is false?

If the condition is false (like in step 3), t.Error is not called, so the test passes silently.

Why do we pass *testing.T as a parameter?

The *testing.T parameter provides methods like Error to report failures, as used in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of 'result' after step 2?

A 5

B undefined

C 0

D error

💡 Hint

Check the 'Evaluation' and 'Result' columns in row 2 of the execution_table.

At which step does the test report an error if the result is wrong?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Action' and 'Evaluation' columns in step 3 where the condition is checked.

If the Add function returned 4 instead of 5, what would happen in the execution_table?

A Test function would not run

B Step 3 condition would be true and t.Error called

C Step 2 would fail to assign result

D Test would pass anyway

💡 Hint

Refer to step 3 where the condition checks if result != 5.

Concept Snapshot

func TestXxx(t *testing.T) {
  result := FunctionToTest(args)
  if result != expected {
    t.Error("message", result)
  }
}
Run tests with 'go test' command.

Full Transcript

In Go, test functions must start with 'Test' and take a *testing.T parameter. Inside, you call the function you want to test and check its result. If the result is not what you expect, call t.Error to report failure. The test runner runs all such functions and shows pass or fail. This example tests Add(2,3) expecting 5. The execution steps show calling the test, running Add, checking the result, and passing the test if no error is reported.