How Do You Test the Equivalence of Maps in Golang?

Test Equivalence of Maps in Golang

In table-driven tests, it's crucial to assert the equality of two maps. While custom implementations and string conversions can be cumbersome, Golang offers a built-in solution.

Using reflect.DeepEqual

The reflect package provides the DeepEqual function that recursively compares values, including maps. It checks:

• Nil values
• Map lengths
• Key-value pairs

import "reflect"

eq := reflect.DeepEqual(m1, m2)

This comprehensive comparison ensures accurate equality testing for maps of any type (e.g., map[string]bool, map[struct{}]interface{}). Note that it requires interface types as arguments.

Implementation Details

The source code for reflect.DeepEqual's Map case reveals:

if p, ok := v1.(reflect.Map); ok && q, ok := v2.(reflect.Map) {
    if p.Len() != q.Len() {
        return false
    }
    for _, k := range p.Keys() {
        if !q.Has(k) || !DeepEqual(p.Elem(k).Interface(), q.Elem(k).Interface()) {
            return false
        }
    }
    return true
}

It verifies nil values, map lengths, and key-value pairs. By passing interface types, it ensures compatibility with various map implementations.

Conclusion

Using reflect.DeepEqual to test map equality in Golang is an idiomatic and efficient solution. It handles all the edge cases and ensures accurate comparison for any type of map. This simplifies table-driven tests and enhances the reliability of your code.

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