Add testcase for multiple expected metrics

Author: DariaKunoichi

prometheus/testutil/testutil_test.go

@@ -331,6 +331,31 @@ func TestScrapeAndCompare(t *testing.T) {
 }
 }
 
+func TestScrapeAndCompareWithMultipleExpected(t *testing.T) {
+const expected = `
+# HELP some_total A value that represents a counter.
+# TYPE some_total counter
+
+some_total{ label1 = "value1" } 1
+
+# HELP some_total2 A value that represents a counter.
+# TYPE some_total2 counter
+
+some_total2{ label1 = "value1" } 1
+`
+
+expectedReader := strings.NewReader(expected)
+
+ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+fmt.Fprintln(w, expected)
+}))
+defer ts.Close()
+
+if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total2"); err != nil {
+t.Errorf("unexpected scraping result:\n%s", err)
+}
+}
+
 func TestScrapeAndCompareFetchingFail(t *testing.T) {
 err := ScrapeAndCompare("some_url", strings.NewReader("some expectation"), "some_total")
 if err == nil {