stackdriver: add tests from regex matching

pkg/tsdb/stackdriver/stackdriver_test.go

@@ -406,6 +406,7 @@ func TestStackdriver(t *testing.T) {
 		})
 
 		Convey("when building filter string", func() {
+			Convey("and theres no regex operator", func() {
 				Convey("and there are wildcards in a filter value", func() {
 					filterParts := []interface{}{"zone", "=", "*-central1*"}
 					value := buildFilterString("somemetrictype", filterParts)
@@ -413,9 +414,23 @@ func TestStackdriver(t *testing.T) {
 				})
 
 				Convey("and there are no wildcards in any filter value", func() {
-				filterParts := []interface{}{"zone", "=", "us-central1-a"}
+					filterParts := []interface{}{"zone", "!=", "us-central1-a"}
 					value := buildFilterString("somemetrictype", filterParts)
-				So(value, ShouldEqual, `metric.type="somemetrictype" zone="us-central1-a"`)
+					So(value, ShouldEqual, `metric.type="somemetrictype" zone!="us-central1-a"`)
+				})
+			})
+
+			Convey("and there is a regex operator", func() {
+				filterParts := []interface{}{"zone", "=~", "us-central1-a~"}
+				value := buildFilterString("somemetrictype", filterParts)
+				Convey("it should remove the ~ character from the operator that belongs to the value", func() {
+					So(value, ShouldNotContainSubstring, `=~`)
+					So(value, ShouldContainSubstring, `zone=`)
+				})
+
+				Convey("it should insert monitoring.regex.full_match before filter value", func() {
+					So(value, ShouldContainSubstring, `zone=monitoring.regex.full_match("us-central1-a~")`)
+				})
 			})
 		})
 	})