encoding/json: modernize tests

There are no changes to what is being tested.
No test cases were removed or added.

Changes made:
* Use a local implementation of test case position marking. See #52751.
* Use consistent names for all test tables and variables.
* Generally speaking, follow modern Go style guide for tests.
* Move global tables local to the test function if possible.
* Make every table entry run in a distinct testing.T.Run.

The purpose of this change is to make it easier to perform
v1-to-v2 development where we want v2 to support close to
bug-for-bug compatibility when running in v1 mode.

Annotating each test case with the location of the test data
makes it easier to jump directly to the test data itself
and understand why this particular case is failing.

Having every test case run in its own t.Run makes it easier
to isolate a particular failing test and work on fixing the code
until that test case starts to pass again.

Unfortunately, many tests are annotated with an empty name.
An empty name is better than nothing, since the testing framework
auto assigns a numeric ID for duplicate names.
It is not worth the trouble to give descriptive names to each
of the thousands of test cases.

Change-Id: I43905f35249b3d77dfca234b9c7808d40e225de8
Reviewed-on: https://go-review.googlesource.com/c/go/+/522880
Auto-Submit: Joseph Tsai <[email protected]>
Run-TryBot: Joseph Tsai <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>
Reviewed-by: Daniel Martí <[email protected]>
Reviewed-by: Bryan Mills <[email protected]>
Reviewed-by: Damien Neil <[email protected]>

Author: dsnet

src/encoding/json/bench_test.go

@@ -93,7 +93,7 @@ func BenchmarkCodeEncoder(b *testing.B) {
 		enc := NewEncoder(io.Discard)
 		for pb.Next() {
 			if err := enc.Encode(&codeStruct); err != nil {
-				b.Fatal("Encode:", err)
+				b.Fatalf("Encode error: %v", err)
 			}
 		}
 	})
@@ -120,10 +120,10 @@ func BenchmarkCodeEncoderError(b *testing.B) {
 		enc := NewEncoder(io.Discard)
 		for pb.Next() {
 			if err := enc.Encode(&codeStruct); err != nil {
-				b.Fatal("Encode:", err)
+				b.Fatalf("Encode error: %v", err)
 			}
 			if _, err := Marshal(dummy); err == nil {
-				b.Fatal("expect an error here")
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	})
@@ -140,7 +140,7 @@ func BenchmarkCodeMarshal(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if _, err := Marshal(&codeStruct); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 		}
 	})
@@ -166,10 +166,10 @@ func BenchmarkCodeMarshalError(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if _, err := Marshal(&codeStruct); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 			if _, err := Marshal(dummy); err == nil {
-				b.Fatal("expect an error here")
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	})
@@ -188,7 +188,7 @@ func benchMarshalBytes(n int) func(*testing.B) {
 	return func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			if _, err := Marshal(v); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 		}
 	}
@@ -215,10 +215,10 @@ func benchMarshalBytesError(n int) func(*testing.B) {
 	return func(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			if _, err := Marshal(v); err != nil {
-				b.Fatal("Marshal:", err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 			if _, err := Marshal(dummy); err == nil {
-				b.Fatal("expect an error here")
+				b.Fatal("Marshal error: got nil, want non-nil")
 			}
 		}
 	}
@@ -280,7 +280,7 @@ func BenchmarkCodeDecoder(b *testing.B) {
 			buf.WriteByte('\n')
 			buf.WriteByte('\n')
 			if err := dec.Decode(&r); err != nil {
-				b.Fatal("Decode:", err)
+				b.Fatalf("Decode error: %v", err)
 			}
 		}
 	})
@@ -297,7 +297,7 @@ func BenchmarkUnicodeDecoder(b *testing.B) {
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
 		if err := dec.Decode(&out); err != nil {
-			b.Fatal("Decode:", err)
+			b.Fatalf("Decode error: %v", err)
 		}
 		r.Seek(0, 0)
 	}
@@ -311,7 +311,7 @@ func BenchmarkDecoderStream(b *testing.B) {
 	buf.WriteString(`"` + strings.Repeat("x", 1000000) + `"` + "\n\n\n")
 	var x any
 	if err := dec.Decode(&x); err != nil {
-		b.Fatal("Decode:", err)
+		b.Fatalf("Decode error: %v", err)
 	}
 	ones := strings.Repeat(" 1\n", 300000) + "\n\n\n"
 	b.StartTimer()
@@ -320,8 +320,11 @@ func BenchmarkDecoderStream(b *testing.B) {
 			buf.WriteString(ones)
 		}
 		x = nil
-		if err := dec.Decode(&x); err != nil || x != 1.0 {
-			b.Fatalf("Decode: %v after %d", err, i)
+		switch err := dec.Decode(&x); {
+		case err != nil:
+			b.Fatalf("Decode error: %v", err)
+		case x != 1.0:
+			b.Fatalf("Decode: got %v want 1.0", i)
 		}
 	}
 }
@@ -337,7 +340,7 @@ func BenchmarkCodeUnmarshal(b *testing.B) {
 		for pb.Next() {
 			var r codeResponse
 			if err := Unmarshal(codeJSON, &r); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -355,7 +358,7 @@ func BenchmarkCodeUnmarshalReuse(b *testing.B) {
 		var r codeResponse
 		for pb.Next() {
 			if err := Unmarshal(codeJSON, &r); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -369,7 +372,7 @@ func BenchmarkUnmarshalString(b *testing.B) {
 		var s string
 		for pb.Next() {
 			if err := Unmarshal(data, &s); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -382,7 +385,7 @@ func BenchmarkUnmarshalFloat64(b *testing.B) {
 		var f float64
 		for pb.Next() {
 			if err := Unmarshal(data, &f); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -395,7 +398,7 @@ func BenchmarkUnmarshalInt64(b *testing.B) {
 		var x int64
 		for pb.Next() {
 			if err := Unmarshal(data, &x); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -408,7 +411,7 @@ func BenchmarkUnmarshalMap(b *testing.B) {
 		x := make(map[string]string, 3)
 		for pb.Next() {
 			if err := Unmarshal(data, &x); err != nil {
-				b.Fatal("Unmarshal:", err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -421,7 +424,7 @@ func BenchmarkIssue10335(b *testing.B) {
 		var s struct{}
 		for pb.Next() {
 			if err := Unmarshal(j, &s); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -437,7 +440,7 @@ func BenchmarkIssue34127(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if _, err := Marshal(&j); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Marshal error: %v", err)
 			}
 		}
 	})
@@ -450,7 +453,7 @@ func BenchmarkUnmapped(b *testing.B) {
 		var s struct{}
 		for pb.Next() {
 			if err := Unmarshal(j, &s); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Unmarshal error: %v", err)
 			}
 		}
 	})
@@ -533,7 +536,7 @@ func BenchmarkEncodeMarshaler(b *testing.B) {
 
 		for pb.Next() {
 			if err := enc.Encode(&m); err != nil {
-				b.Fatal("Encode:", err)
+				b.Fatalf("Encode error: %v", err)
 			}
 		}
 	})
@@ -548,7 +551,7 @@ func BenchmarkEncoderEncode(b *testing.B) {
 	b.RunParallel(func(pb *testing.PB) {
 		for pb.Next() {
 			if err := NewEncoder(io.Discard).Encode(v); err != nil {
-				b.Fatal(err)
+				b.Fatalf("Encode error: %v", err)
 			}
 		}
 	})