diff --git a/prometheus/counter_test.go b/prometheus/counter_test.go
index b2023f0..e11b97e 100644
--- a/prometheus/counter_test.go
+++ b/prometheus/counter_test.go
@@ -28,7 +28,7 @@ func testCounter(t tester) {
 				steps: []func(g Counter){},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[]}",
+				value: `{"type":"counter","value":[]}`,
 			},
 		},
 		{
@@ -40,7 +40,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{},\"value\":1}]}",
+				value: `{"type":"counter","value":[{"labels":{},"value":1}]}`,
 			},
 		},
 		{
@@ -52,7 +52,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{},\"value\":2}]}",
+				value: `{"type":"counter","value":[{"labels":{},"value":2}]}`,
 			},
 		},
 		{
@@ -67,7 +67,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{},\"value\":5}]}",
+				value: `{"type":"counter","value":[{"labels":{},"value":5}]}`,
 			},
 		},
 		{
@@ -85,7 +85,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[]}",
+				value: `{"type":"counter","value":[]}`,
 			},
 		},
 		{
@@ -97,7 +97,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":19}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":19}]}`,
 			},
 		},
 		{
@@ -112,7 +112,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":24}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":24}]}`,
 			},
 		},
 		{
@@ -124,7 +124,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":1}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":1}]}`,
 			},
 		},
 		{
@@ -136,7 +136,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":-1}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":-1}]}`,
 			},
 		},
 		{
@@ -151,7 +151,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":28}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":28}]}`,
 			},
 		},
 		{
@@ -166,7 +166,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":36}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":36}]}`,
 			},
 		},
 		{
@@ -181,7 +181,7 @@ func testCounter(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"counter\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":27}]}",
+				value: `{"type":"counter","value":[{"labels":{"handler":"/foo"},"value":27}]}`,
 			},
 		},
 	}
diff --git a/prometheus/gauge_test.go b/prometheus/gauge_test.go
index 8e7e5f1..ee3d425 100644
--- a/prometheus/gauge_test.go
+++ b/prometheus/gauge_test.go
@@ -28,7 +28,7 @@ func testGauge(t tester) {
 				steps: []func(g Gauge){},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[]}",
+				value: `{"type":"gauge","value":[]}`,
 			},
 		},
 		{
@@ -40,7 +40,7 @@ func testGauge(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[{\"labels\":{},\"value\":1}]}",
+				value: `{"type":"gauge","value":[{"labels":{},"value":1}]}`,
 			},
 		},
 		{
@@ -52,7 +52,7 @@ func testGauge(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[{\"labels\":{},\"value\":2}]}",
+				value: `{"type":"gauge","value":[{"labels":{},"value":2}]}`,
 			},
 		},
 		{
@@ -67,7 +67,7 @@ func testGauge(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[{\"labels\":{},\"value\":5}]}",
+				value: `{"type":"gauge","value":[{"labels":{},"value":5}]}`,
 			},
 		},
 		{
@@ -85,7 +85,7 @@ func testGauge(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[]}",
+				value: `{"type":"gauge","value":[]}`,
 			},
 		},
 		{
@@ -97,7 +97,7 @@ func testGauge(t tester) {
 				},
 			},
 			out: output{
-				value: "{\"type\":\"gauge\",\"value\":[{\"labels\":{\"handler\":\"/foo\"},\"value\":19}]}",
+				value: `{"type":"gauge","value":[{"labels":{"handler":"/foo"},"value":19}]}`,
 			},
 		},
 	}
diff --git a/prometheus/registry_test.go b/prometheus/registry_test.go
index df0f1c2..b1d8379 100644
--- a/prometheus/registry_test.go
+++ b/prometheus/registry_test.go
@@ -282,7 +282,7 @@ func testDumpToWriter(t tester) {
 					"foo": NewCounter(),
 				},
 			},
-			out: []byte("[{\"baseLabels\":{\"label_foo\":\"foo\",\"name\":\"foo\"},\"docstring\":\"metric foo\",\"metric\":{\"type\":\"counter\",\"value\":[]}}]"),
+			out: []byte(`[{"baseLabels":{"label_foo":"foo","name":"foo"},"docstring":"metric foo","metric":{"type":"counter","value":[]}}]`),
 		},
 		{
 			in: input{
@@ -291,7 +291,7 @@ func testDumpToWriter(t tester) {
 					"bar": NewCounter(),
 				},
 			},
-			out: []byte("[{\"baseLabels\":{\"label_bar\":\"bar\",\"name\":\"bar\"},\"docstring\":\"metric bar\",\"metric\":{\"type\":\"counter\",\"value\":[]}},{\"baseLabels\":{\"label_foo\":\"foo\",\"name\":\"foo\"},\"docstring\":\"metric foo\",\"metric\":{\"type\":\"counter\",\"value\":[]}}]"),
+			out: []byte(`[{"baseLabels":{"label_bar":"bar","name":"bar"},"docstring":"metric bar","metric":{"type":"counter","value":[]}},{"baseLabels":{"label_foo":"foo","name":"foo"},"docstring":"metric foo","metric":{"type":"counter","value":[]}}]`),
 		},
 	}