encoding/json: cleanup tests

Perform minor cleanups in tests to improve printout of diffs
and/or follow modern coding style.

This reduces the amount of diffs between v1 and the v2 prototype.

Change-Id: I019bb9642e2135f2fa3eac6abfa6df91c397aa82
Reviewed-on: https://go-review.googlesource.com/c/go/+/642257
Reviewed-by: Damien Neil <[email protected]>
Auto-Submit: Joseph Tsai <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: dsnet

src/encoding/json/decode_test.go

@@ -1321,7 +1321,7 @@ func TestUnmarshal(t *testing.T) {
 			var scan scanner
 			if err := checkValid(in, &scan); err != nil {
 				if !equalError(err, tt.err) {
-					t.Fatalf("%s: checkValid error: %#v", tt.Where, err)
+					t.Fatalf("%s: checkValid error:\n\tgot  %#v\n\twant %#v", tt.Where, err, tt.err)
 				}
 			}
 			if tt.ptr == nil {
@@ -1355,7 +1355,7 @@ func TestUnmarshal(t *testing.T) {
 				dec.DisallowUnknownFields()
 			}
 			if err := dec.Decode(v.Interface()); !equalError(err, tt.err) {
-				t.Fatalf("%s: Decode error:\n\tgot:  %#v\n\twant: %#v", tt.Where, err, tt.err)
+				t.Fatalf("%s: Decode error:\n\tgot:  %v\n\twant: %v\n\n\tgot:  %#v\n\twant: %#v", tt.Where, err, tt.err, err, tt.err)
 			} else if err != nil && tt.out == nil {
 				// Initialize tt.out during an error where there are no mutations,
 				// so the output is just the zero value of the input type.

src/encoding/json/stream_test.go

@@ -79,9 +79,9 @@ func TestEncoder(t *testing.T) {
 				t.Fatalf("#%d.%d Encode error: %v", i, j, err)
 			}
 		}
-		if have, want := buf.String(), nlines(streamEncoded, i); have != want {
+		if got, want := buf.String(), nlines(streamEncoded, i); got != want {
 			t.Errorf("encoding %d items: mismatch:", i)
-			diff(t, []byte(have), []byte(want))
+			diff(t, []byte(got), []byte(want))
 			break
 		}
 	}
@@ -148,9 +148,9 @@ func TestEncoderIndent(t *testing.T) {
 	for _, v := range streamTest {
 		enc.Encode(v)
 	}
-	if have, want := buf.String(), streamEncodedIndent; have != want {
-		t.Error("Encode mismatch:")
-		diff(t, []byte(have), []byte(want))
+	if got, want := buf.String(), streamEncodedIndent; got != want {
+		t.Errorf("Encode mismatch:\ngot:\n%s\n\nwant:\n%s", got, want)
+		diff(t, []byte(got), []byte(want))
 	}
 }
 

src/encoding/json/tags_test.go

@@ -4,9 +4,7 @@
 
 package json
 
-import (
-	"testing"
-)
+import "testing"
 
 func TestTagParsing(t *testing.T) {
 	name, opts := parseTag("field,foobar,foo")