Cause a failure when field's documented and actual types do not match

Closes gh-276

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/RequestFieldsSnippetFailureTests.java

@@ -110,6 +110,33 @@ public class RequestFieldsSnippetFailureTests {
 								.build());
 	}
 
+	@Test
+	public void fieldWithExplicitTypeThatDoesNotMatchThePayload() throws IOException {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		this.thrown.expectMessage(equalTo("The documented type of the field 'a' is"
+				+ " Object but the actual type is Number"));
+		new RequestFieldsSnippet(Arrays
+				.asList(fieldWithPath("a").description("one").type(JsonFieldType.OBJECT)))
+						.document(new OperationBuilder("mismatched-field-types",
+								this.snippet.getOutputDirectory())
+										.request("http://localhost")
+										.content("{ \"a\": 5 }").build());
+	}
+
+	@Test
+	public void fieldWithExplicitSpecificTypeThatActuallyVaries() throws IOException {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		this.thrown.expectMessage(equalTo("The documented type of the field '[].a' is"
+				+ " Object but the actual type is Varies"));
+		new RequestFieldsSnippet(Arrays.asList(
+				fieldWithPath("[].a").description("one").type(JsonFieldType.OBJECT)))
+						.document(new OperationBuilder("mismatched-field-types",
+								this.snippet.getOutputDirectory())
+										.request("http://localhost")
+										.content("[{ \"a\": 5 },{ \"a\": \"b\" }]")
+										.build());
+	}
+
 	@Test
 	public void undocumentedXmlRequestField() throws IOException {
 		this.thrown.expect(SnippetException.class);

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/RequestFieldsSnippetTests.java

@@ -177,6 +177,34 @@ public class RequestFieldsSnippetTests extends AbstractSnippetTests {
 												.build());
 	}
 
+	@Test
+	public void fieldWithExplictExactlyMatchingType() throws IOException {
+		this.snippet
+				.expectRequestFields("request-field-with-explicit-exactly-matching-type")
+				.withContents(tableWithHeader("Path", "Type", "Description").row("`a`",
+						"`Number`", "one"));
+
+		new RequestFieldsSnippet(Arrays
+				.asList(fieldWithPath("a").description("one").type(JsonFieldType.NUMBER)))
+						.document(operationBuilder(
+								"request-field-with-explicit-exactly-matching-type")
+										.request("http://localhost")
+										.content("{\"a\": 5 }").build());
+	}
+
+	@Test
+	public void fieldWithExplictVariesType() throws IOException {
+		this.snippet.expectRequestFields("request-field-with-explicit-varies-type")
+				.withContents(tableWithHeader("Path", "Type", "Description").row("`a`",
+						"`Varies`", "one"));
+
+		new RequestFieldsSnippet(Arrays.asList(fieldWithPath("a").description("one")
+				.type(JsonFieldType.VARIES))).document(
+						operationBuilder("request-field-with-explicit-varies-type")
+								.request("http://localhost").content("{\"a\": 5 }")
+								.build());
+	}
+
 	@Test
 	public void xmlRequestFields() throws IOException {
 		this.snippet.expectRequestFields("xml-request")

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/ResponseFieldsSnippetFailureTests.java

@@ -57,8 +57,32 @@ public class ResponseFieldsSnippetFailureTests {
 				equalTo("Cannot document response fields as the response body is empty"));
 		new ResponseFieldsSnippet(Arrays.asList(fieldWithPath("a").description("one")))
 				.document(new OperationBuilder("no-response-body",
-						this.snippet.getOutputDirectory()).request("http://localhost")
-								.build());
+						this.snippet.getOutputDirectory()).build());
+	}
+
+	@Test
+	public void fieldWithExplicitTypeThatDoesNotMatchThePayload() throws IOException {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		this.thrown.expectMessage(equalTo("The documented type of the field 'a' is"
+				+ " Object but the actual type is Number"));
+		new ResponseFieldsSnippet(Arrays
+				.asList(fieldWithPath("a").description("one").type(JsonFieldType.OBJECT)))
+						.document(new OperationBuilder("mismatched-field-types",
+								this.snippet.getOutputDirectory()).response()
+										.content("{ \"a\": 5 }}").build());
+	}
+
+	@Test
+	public void fieldWithExplicitSpecificTypeThatActuallyVaries() throws IOException {
+		this.thrown.expect(FieldTypesDoNotMatchException.class);
+		this.thrown.expectMessage(equalTo("The documented type of the field '[].a' is"
+				+ " Object but the actual type is Varies"));
+		new ResponseFieldsSnippet(Arrays.asList(
+				fieldWithPath("[].a").description("one").type(JsonFieldType.OBJECT)))
+						.document(new OperationBuilder("mismatched-field-types",
+								this.snippet.getOutputDirectory()).response()
+										.content("[{ \"a\": 5 },{ \"a\": \"b\" }]")
+										.build());
 	}
 
 	@Test

spring-restdocs-core/src/test/java/org/springframework/restdocs/payload/ResponseFieldsSnippetTests.java

@@ -185,6 +185,33 @@ public class ResponseFieldsSnippetTests extends AbstractSnippetTests {
 										.build());
 	}
 
+	@Test
+	public void fieldWithExplictExactlyMatchingType() throws IOException {
+		this.snippet
+				.expectResponseFields(
+						"response-field-with-explicit-exactly-matching-type")
+				.withContents(tableWithHeader("Path", "Type", "Description").row("`a`",
+						"`Number`", "one"));
+
+		new ResponseFieldsSnippet(Arrays
+				.asList(fieldWithPath("a").description("one").type(JsonFieldType.NUMBER)))
+						.document(operationBuilder(
+								"response-field-with-explicit-exactly-matching-type")
+										.response().content("{\"a\": 5 }").build());
+	}
+
+	@Test
+	public void fieldWithExplictVariesType() throws IOException {
+		this.snippet.expectResponseFields("response-field-with-explicit-varies-type")
+				.withContents(tableWithHeader("Path", "Type", "Description").row("`a`",
+						"`Varies`", "one"));
+
+		new ResponseFieldsSnippet(Arrays.asList(fieldWithPath("a").description("one")
+				.type(JsonFieldType.VARIES))).document(
+						operationBuilder("response-field-with-explicit-varies-type")
+								.response().content("{\"a\": 5 }").build());
+	}
+
 	@Test
 	public void xmlResponseFields() throws IOException {
 		this.snippet.expectResponseFields("xml-response")