instana / deep

Golang deep variable equality test that returns human-readable differences

Deep Variable Equality for Humans

This is a fork of go-deep to add some functionality we required for working with our operators.

Original function

This package provides a functions: deep.Equal. It's like reflect.DeepEqual but much friendlier to humans (or any sentient being) for two reason:

• deep.Equal returns a map of differences in the form path-of-difference => actusal difference (the original implementation returned a list of strings)
• deep.Equal does not compare unexported fields (by default)

reflect.DeepEqual is good (like all things Golang!), but it's a game of Hunt the Wumpus. For large maps, slices, and structs, finding the difference is difficult.

deep.Equal doesn't play games with you, it lists the differences:

package main_test

import (
	"testing"
	"github.com/instana/deep"
)

type T struct {
	Name    string
	Numbers []float64
}

func TestDeepEqual(t *testing.T) {
	// Can you spot the difference?
	t1 := T{
		Name:    "Isabella",
		Numbers: []float64{1.13459, 2.29343, 3.010100010},
	}
	t2 := T{
		Name:    "Isabella",
		Numbers: []float64{1.13459, 2.29843, 3.010100010},
	}

	if diff := deep.Equal(t1, t2); diff != nil {
		t.Error(diff)
	}
}

$ go test
--- FAIL: TestDeepEqual (0.00s)
        main_test.go:25: [Numbers.slice[1]: 2.29343 != 2.29843]

The difference is in Numbers.slice[1]: the two values aren't equal using Go ==.

Extended function

This package now provides a function: deep.EqualSubset. This function does a match to verify if the left element is a subset of the right element. It additionally allows to specify that arrays/slices are equal as long as they contain the same elements, even if not in the same order.

package main_test

import (
	"testing"
	"github.com/instana/deep"
)

func Example(t *testing.T) {
	type student struct {
		Name string
		Age  int
		Arr  []string
	}

	left := student{"mark", 10, []string{"same1", "different", "same2"}}
	right := student{"mark", 10, []string{"same1", "same2", "different"}}

	diff, isSame := deep.EqualSubset(left, right, nil, true, false)
}