util: use cmp.Diff to compare structs in tests (google#136)

`cmp.Diff` is a better way to compare two structs since the diff is
easier to read.
This PR improves the tests by replacing `reflect.DeepEqual` with
`cmp.Diff`.

Author: cuixq

util/maven/dependency_test.go

@@ -175,6 +175,6 @@ func TestProcessDependencies(t *testing.T) {
 	}
 	proj.ProcessDependencies(getDependencyManagement)
 	if diff := cmp.Diff(proj, want); diff != "" {
-		t.Errorf("processDependencies: got %v\n, want %v", proj, want)
+		t.Errorf("processDependencies:\n(-got, +want):\n%s", diff)
 	}
 }

util/maven/metadata_test.go

@@ -68,6 +68,6 @@ func TestMetadata(t *testing.T) {
 		t.Fatalf("failed to unmarshal input: %v", err)
 	}
 	if diff := cmp.Diff(got, want); diff != "" {
-		t.Errorf("unmarshal input got: %v,\n want: %v", got, want)
+		t.Errorf("unmarshal input:\n(-got, +want):\n%s", diff)
 	}
 }

util/maven/profile_test.go

@@ -100,7 +100,7 @@ func TestProfile(t *testing.T) {
 		t.Fatalf("failed to unmarshal input: %v", err)
 	}
 	if diff := cmp.Diff(project.Profiles, want); diff != "" {
-		t.Errorf("unmarshal profiles: got %v, want %v", project.Profiles, want)
+		t.Errorf("unmarshal profiles:\n(-got, +want):\n%s", diff)
 	}
 }
 
@@ -486,6 +486,6 @@ func TestMergeProfiles(t *testing.T) {
 	}
 	proj.Profiles = nil
 	if diff := cmp.Diff(proj, want); diff != "" {
-		t.Fatalf("mergeProfiles does not have match result:\n got %v\n want%v\n", proj, want)
+		t.Fatalf("mergeProfiles does not have match result:\n(-got, +want):\n%s", diff)
 	}
 }

util/maven/project_test.go

@@ -207,7 +207,7 @@ func TestProject(t *testing.T) {
 		t.Fatalf("failed to unmarshal input: %v", err)
 	}
 	if diff := cmp.Diff(got, want); diff != "" {
-		t.Errorf("unmarshal input: got %v\n, want %v", got, want)
+		t.Errorf("unmarshal input:\n(- got, + want):\n%s", diff)
 	}
 }
 
@@ -596,7 +596,7 @@ func TestMergeParent(t *testing.T) {
 	}
 	proj2.MergeParent(parent)
 	if diff := cmp.Diff(proj2, want2); diff != "" {
-		t.Errorf("mergeParent: got %v\n, want %v", proj2, want2)
+		t.Errorf("mergeParent:\n(-got, +want):\n%s", diff)
 	}
 }
 
@@ -781,6 +781,6 @@ func TestInterpolate(t *testing.T) {
 	}
 	proj.Interpolate()
 	if diff := cmp.Diff(proj, want); diff != "" {
-		t.Errorf("interpolate: got %v\n, want %v", proj, want)
+		t.Errorf("interpolate:\n(-got, +want):\n%s", diff)
 	}
 }

util/maven/properties_test.go

@@ -92,6 +92,6 @@ func TestPropertyMap(t *testing.T) {
 		t.Fatalf("failed to make property map: %v", err)
 	}
 	if diff := cmp.Diff(got, want); diff != "" {
-		t.Errorf("property map mistmatch: got %v want %v", got, want)
+		t.Errorf("property map mistmatch:\n(-got, +want):\n%s", diff)
 	}
 }

util/resolve/internal/deptest/deptest_test.go

@@ -16,9 +16,10 @@ package deptest
 
 import (
 	"errors"
-	"reflect"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+
 	"deps.dev/util/resolve/dep"
 )
 
@@ -142,8 +143,14 @@ func TestParseStringErrors(t *testing.T) {
 	}
 
 	for _, c := range cases {
-		if _, err := ParseString(c.s); !reflect.DeepEqual(err, c.err) {
-			t.Errorf("unexpected error for %s:\n got: %v\nwant: %v", c.s, err, c.err)
+		_, err := ParseString(c.s)
+		if diff := cmp.Diff(err, c.err, cmp.Comparer(func(x, y error) bool {
+			if x == nil || y == nil {
+				return x == nil && y == nil
+			}
+			return x.Error() == y.Error()
+		})); diff != "" {
+			t.Errorf("unexpected error for %s:\n(-got, +want):\n%s", c.s, diff)
 		}
 	}
 }

util/resolve/internal/resolvetest/resolvetest_test.go

@@ -16,7 +16,6 @@ package resolvetest
 
 import (
 	"context"
-	"reflect"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -56,7 +55,7 @@ func TestParseData(t *testing.T) {
 	}
 	g1, g2 := a.Graph["alice"], a.Graph["alice2"]
 	if d := cmp.Diff(g1, g2); d != "" {
-		t.Logf("Mismatching parsed graphs:(- alice, + alice1):\n%s", d)
+		t.Logf("Mismatching parsed graphs:(-alice, +alice2):\n%s", d)
 	}
 
 	if got, want := len(a.Test), 2; got != want {
@@ -97,8 +96,9 @@ func TestParseData(t *testing.T) {
 		t.Fatalf("Unexpected graph name: got %q, want %q", got, want)
 	}
 
-	if got, want := a.Test[0].Flags, map[string]bool{"flag1": true, "flag2": true}; !reflect.DeepEqual(got, want) {
-		t.Fatalf("Unexpected test flags,\n got %v\nwant %v", got, want)
+	got, want := a.Test[0].Flags, map[string]bool{"flag1": true, "flag2": true}
+	if diff := cmp.Diff(got, want); diff != "" {
+		t.Errorf("Unexpected test flags:\n(-got, +want):\n%s", diff)
 	}
 
 	// Multiverse with overlap.

util/resolve/internal/versiontest/versiontest_test.go

@@ -16,9 +16,10 @@ package versiontest
 
 import (
 	"errors"
-	"reflect"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+
 	"deps.dev/util/resolve/version"
 )
 
@@ -102,8 +103,14 @@ func TestParseStringErrors(t *testing.T) {
 	}
 
 	for _, c := range cases {
-		if _, err := ParseString(c.s); !reflect.DeepEqual(err, c.err) {
-			t.Errorf("unexpected error for %s:\n got: %v\nwant: %v", c.s, err, c.err)
+		_, err := ParseString(c.s)
+		if diff := cmp.Diff(err, c.err, cmp.Comparer(func(x, y error) bool {
+			if x == nil || y == nil {
+				return x == nil && y == nil
+			}
+			return x.Error() == y.Error()
+		})); diff != "" {
+			t.Errorf("unexpected error for %s:\n(-got, +want):\n%s", c.s, diff)
 		}
 	}
 }

util/resolve/match_test.go

@@ -16,10 +16,11 @@ package resolve
 
 import (
 	"math/rand"
-	"reflect"
 	"strings"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
+
 	"deps.dev/util/resolve/dep"
 	"deps.dev/util/resolve/version"
 )
@@ -52,8 +53,8 @@ func TestSortVersions(t *testing.T) {
 				got[i], got[j] = got[j], got[i]
 			})
 			SortVersions(got)
-			if !reflect.DeepEqual(got, vs) {
-				t.Errorf("SortVersions:\nwant: %v\n got: %v", vs, got)
+			if diff := cmp.Diff(got, vs); diff != "" {
+				t.Errorf("SortVersions:\n(-got, +want):\n%s", diff)
 			}
 		}
 	}
@@ -115,8 +116,8 @@ func TestSortNPMDependencies(t *testing.T) {
 				got[i], got[j] = got[j], got[i]
 			})
 			SortDependencies(got)
-			if !reflect.DeepEqual(got, want) {
-				t.Errorf("SortDependencies:\n got: %v\nwant %v", got, want)
+			if diff := cmp.Diff(got, want); diff != "" {
+				t.Errorf("SortDependencies:\n(-got, +want):\n%s", diff)
 			}
 		}
 	}
@@ -263,8 +264,8 @@ func TestMatchNPMRequirement(t *testing.T) {
 		if got == nil {
 			got = []Version{}
 		}
-		if !reflect.DeepEqual(got, c.want) {
-			t.Errorf("matchNPMRequirement(%v):\nwant: %v\n got: %v", c.req, c.want, got)
+		if diff := cmp.Diff(got, c.want); diff != "" {
+			t.Errorf("matchNPMRequirement(%v):\n(-got, +want):\n%s", c.req, diff)
 		}
 	}
 }

util/resolve/maven_test.go

@@ -16,7 +16,6 @@ package resolve
 
 import (
 	"context"
-	"reflect"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
@@ -130,8 +129,8 @@ func TestMavenVersion(t *testing.T) {
 			VersionKey: vk,
 			AttrSet:    test.attr,
 		}
-		if !reflect.DeepEqual(got, want) {
-			t.Errorf("Version(%v):\ngot: %v\nwant: %v\n", vk, got, want)
+		if diff := cmp.Diff(got, want); diff != "" {
+			t.Errorf("Version(%v):\n(-got, +want):\n%s", vk, diff)
 		}
 	}
 }
@@ -250,7 +249,7 @@ func TestMavenRequirements(t *testing.T) {
 		},
 	}
 	if d := cmp.Diff(want, got); d != "" {
-		t.Errorf("mavenRequirements:\n(- want, + got):\n%s", d)
+		t.Errorf("mavenRequirements:\n(-want, +got):\n%s", d)
 	}
 }