Unit testing in golang function error handling

Unit testing Function error handling methods in the Go language include: Create simulated input: Create a simulated object with controlled errors. Assert error message: Match the returned error message with the expected message. Cover Error Conditions: Write test cases for all possible error conditions.

Unit testing in Go language function error handling

Background

In In Go language, errors in functions are handled by checking the value of type error. To ensure correct error handling, it is crucial to perform unit tests.

Unit Testing Strategies

The following strategy is very effective when unit testing error handling in functions:

• Create Mock as input: Create mock objects (for example, simulate file system or network calls) that return controlled errors.
• Assert error messages: Use an assertion library such as assert.Equal() to verify that the returned error message matches the expected error message.
• Covering Error Conditions: Write test cases for every possible error condition. This will ensure that the error handling logic works as expected in all cases.

Practical case

Consider the following function that calculates the sum of two numbers:

func Sum(a, b int) (int, error) {
    if a < 0 || b < 0 {
        return 0, errors.New("non-negative integers only")
    }
    return a + b, nil
}

Unit test

import (
    "errors"
    "testing"
)

func TestSum(t *testing.T) {
    tests := []struct {
        a, b int
        expected int
        err error
    }{
        {a: 1, b: 2, expected: 3, err: nil},
        {a: -1, b: 2, expected: 0, err: errors.New("non-negative integers only")},
    }

    for _, tt := range tests {
        t.Run("test", func(t *testing.T) {
            sum, err := Sum(tt.a, tt.b)
            if sum != tt.expected {
                t.Errorf("Expected %d, got %d", tt.expected, sum)
            }
            if !errors.Is(err, tt.err) {
                t.Errorf("Expected error %q, got %q", tt.err, err)
            }
        })
    }
}

Conclusion

Function error handling in Go can be effectively tested using simulated inputs, error message assertions, and exhaustive test case coverage. This helps ensure that the code is robust and reliable.

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