Add tests for attribute JSON marshalling

attribute/set_test.go

@@ -348,6 +348,55 @@ func args(m reflect.Method) []reflect.Value {
 	return out
 }
 
+func TestMarshalJSON(t *testing.T) {
+	for _, tc := range []struct {
+		desc     string
+		kvs      []attribute.KeyValue
+		wantJSON string
+	}{
+		{
+			desc:     "empty",
+			kvs:      []attribute.KeyValue{},
+			wantJSON: `[]`,
+		},
+		{
+			desc:     "single string attribute",
+			kvs:      []attribute.KeyValue{attribute.String("A", "a")},
+			wantJSON: `[{"Key":"A","Value":{"Type":"STRING","Value":"a"}}]`,
+		},
+		{
+			desc: "many mixed attributes",
+			kvs: []attribute.KeyValue{
+				attribute.Bool("A", true),
+				attribute.BoolSlice("B", []bool{true, false}),
+				attribute.Int("C", 1),
+				attribute.IntSlice("D", []int{2, 3}),
+				attribute.Int64("E", 22),
+				attribute.Int64Slice("F", []int64{33, 44}),
+				attribute.Float64("G", 1.1),
+				attribute.Float64Slice("H", []float64{2.2, 3.3}),
+				attribute.String("I", "Z"),
+				attribute.StringSlice("J", []string{"X", "Y"}),
+				attribute.Stringer("K", &simpleStringer{val: "foo"}),
+			},
+			wantJSON: `[{"Key":"A","Value":{"Type":"BOOL","Value":true}},{"Key":"B","Value":{"Type":"BOOLSLICE","Value":[true,false]}},{"Key":"C","Value":{"Type":"INT64","Value":1}},{"Key":"D","Value":{"Type":"INT64SLICE","Value":[2,3]}},{"Key":"E","Value":{"Type":"INT64","Value":22}},{"Key":"F","Value":{"Type":"INT64SLICE","Value":[33,44]}},{"Key":"G","Value":{"Type":"FLOAT64","Value":1.1}},{"Key":"H","Value":{"Type":"FLOAT64SLICE","Value":[2.2,3.3]}},{"Key":"I","Value":{"Type":"STRING","Value":"Z"}},{"Key":"J","Value":{"Type":"STRINGSLICE","Value":["X","Y"]}},{"Key":"K","Value":{"Type":"STRING","Value":"foo"}}]`,
+		},
+	} {
+		t.Run(tc.desc, func(t *testing.T) {
+			set := attribute.NewSet(tc.kvs...)
+			by, err := set.MarshalJSON()
+			require.NoError(t, err)
+			assert.JSONEq(t, tc.wantJSON, string(by))
+		})
+	}
+}
+
+type simpleStringer struct {
+	val string
+}
+
+func (s *simpleStringer) String() string { return s.val }
+
 func BenchmarkFiltering(b *testing.B) {
 	var kvs [26]attribute.KeyValue
 	buf := [1]byte{'A' - 1}