Ensures that regex is asserted also for RegexProperty not only Pattern

fixes gh-1200

spring-cloud-contract-spec/src/main/groovy/org/springframework/cloud/contract/spec/internal/Common.groovy

@@ -244,6 +244,14 @@ class Common {
 		assert value ==~ pattern
 	}
 
+	void assertThatSidesMatch(RegexProperty pattern, String value) {
+		assert value ==~ pattern.pattern
+	}
+
+	void assertThatSidesMatch(String value, RegexProperty pattern) {
+		assert value ==~ pattern.pattern
+	}
+
 	void assertThatSidesMatch(MatchingStrategy firstSide, MatchingStrategy secondSide) {
 		if (firstSide.type == MatchingStrategy.Type.ABSENT && secondSide.type != MatchingStrategy.Type.ABSENT) {
 			throwAbsentError()

spring-cloud-contract-spec/src/test/groovy/org/springframework/cloud/contract/spec/internal/ContractSpec.groovy

@@ -16,6 +16,7 @@
 
 package org.springframework.cloud.contract.spec.internal
 
+import spock.lang.Issue
 import spock.lang.Specification
 
 import org.springframework.cloud.contract.spec.Contract
@@ -422,4 +423,23 @@ then:
 		expect:
 			contract != null
 	}
+
+	@Issue("1200")
+	def 'should fail when regex do not match the concrete value'() {
+		when:
+			Contract.make {
+				request {
+					method 'GET'
+					url '/any'
+				}
+				response {
+					status OK()
+					body([
+							time: $(p(regex(iso8601WithOffset())),c( "thisIsNotADate"))
+					])
+				}
+			}
+		then:
+			thrown(AssertionError)
+	}
 }