Implement Request.Equal() method

Implement Request.Equal(), include a basic check that it's working
correctly, and check that cmp.Diff can consume two requests and
compare them.

Signed-off-by: Greg NISBET <gregory.nisbet@gmail.com>

Author: gregory-nisbet

types/authorize.go

@@ -11,6 +11,14 @@ type Request struct {
 	Context   Record    `json:"context"`
 }
 
+// Equal comapres two requests for sameness
+func (r Request) Equal(other Request) bool {
+	return (r.Principal == other.Principal &&
+		r.Action == other.Action &&
+		r.Resource == other.Resource &&
+		r.Context.Equal(other.Context))
+}
+
 // A Decision is the result of the authorization.
 type Decision bool
 

types/authorize_test.go

@@ -5,6 +5,7 @@ import (
 	"testing"
 
 	"github.com/cedar-policy/cedar-go/internal/testutil"
+	"github.com/google/go-cmp/cmp"
 )
 
 func TestJSONDecision(t *testing.T) {
@@ -39,6 +40,60 @@ func TestJSONDecision(t *testing.T) {
 	})
 }
 
+func TestRequestEqual(t *testing.T) {
+	t.Parallel()
+
+	testcases := []Request{
+		{},
+		{
+			Principal: EntityUID{
+				Type: "a",
+				ID:   "b",
+			},
+		},
+		{
+			Action: EntityUID{
+				Type: "a",
+				ID:   "b",
+			},
+		},
+		{
+			Resource: EntityUID{
+				Type: "a",
+				ID:   "b",
+			},
+		},
+		{
+			Context: NewRecord(RecordMap{
+				"a": Long(42),
+			}),
+		},
+	}
+
+	for i, r := range testcases {
+		for j, s := range testcases[:i] {
+			expected := i == j
+			actual := r.Equal(s)
+			if actual != s.Equal(r) {
+				t.Errorf("Request.Equal not symmetric for examples #%d and #%d, actual=%v, expected=%v", i, j, actual, expected)
+			}
+			if actual != expected {
+				t.Errorf("Request.Equal returned unexpected result for #%d and #%d, actual=%v, expected=%v", i, j, actual, expected)
+			}
+		}
+	}
+}
+
+func TestRequestEqualSupportsCmpDiff(t *testing.T) {
+	t.Parallel()
+
+	// This test is not very interesting, we just want to make
+	// sure that it compiles.
+	if diff := cmp.Diff(Record{}, Record{}); diff != "" {
+		t.Errorf("unexpected diff (-want +got): %s", diff)
+	}
+}
+
 func TestError(t *testing.T) {
 	t.Parallel()
 	e := DiagnosticError{PolicyID: "policy42", Message: "bad error"}