From 1e34aaf536cdb1f92f49205a0f9df55f38d97a3d Mon Sep 17 00:00:00 2001
From: Matthew Hague <matthew.hague@rhul.ac.uk>
Date: Wed, 9 Dec 2020 19:32:46 +0000
Subject: [PATCH] Add call and callStatic that check null return
You can define if a null return value is considered an error. Useful if
you need to use the returned object later on in the test.
---
.../uk/ac/rhul/cs/javatester/CodeTester.java | 129 +++++++++++++++---
.../uk/ac/rhul/cs/javatester/UnitTests.java | 30 ++++
.../cs/javatester/solution/NullPtrMethod.java | 4 +
3 files changed, 147 insertions(+), 16 deletions(-)
diff --git a/src/main/java/uk/ac/rhul/cs/javatester/CodeTester.java b/src/main/java/uk/ac/rhul/cs/javatester/CodeTester.java
index d6968a9..2ecad55 100644
--- a/src/main/java/uk/ac/rhul/cs/javatester/CodeTester.java
+++ b/src/main/java/uk/ac/rhul/cs/javatester/CodeTester.java
@@ -302,7 +302,6 @@ public class CodeTester {
return array;
}
-
/**
* Convenience for constructMsg with default messages
*/
@@ -325,6 +324,23 @@ public class CodeTester {
return constructMsg(msg, invokeMsg, className, params);
}
+ /**
+ * Convenience for callMsgAcceptNull with acceptNull set to true
+ */
+ public Object callMsg(String msg,
+ String invocationMsg,
+ Object o,
+ String methodName,
+ Object... params) throws
+ BaseTester.FailedTestException {
+ return callMsgAcceptNull(msg,
+ invocationMsg,
+ true,
+ o,
+ methodName,
+ params);
+ }
+
/**
* Attempts to call an object method
*
@@ -332,20 +348,24 @@ public class CodeTester {
* msg and invocationMsg can contain LOG_EXPAND which will be replaced by
* getIndentedLinesString in the exception.
*
+ * Can specify whether to cause a failure if the method returns null
+ *
* @param msg the failure message
* @param invocationMsg failure message prefix in case method call
* throws exception (student code fails)
+ * @param acceptNull whether the result of the call can be null
* @param o the object to call the method on
* @param String name method name
* @param parameterTypes the arguments (cannot be null else type
* can't be inferred, with throw NPE)
* @return the result object
*/
- public Object callMsg(String msg,
- String invocationMsg,
- Object o,
- String methodName,
- Object... params) throws
+ public Object callMsgAcceptNull(String msg,
+ String invocationMsg,
+ boolean acceptNull,
+ Object o,
+ String methodName,
+ Object... params) throws
BaseTester.FailedTestException {
Class<?>[] parameterTypes
= Stream.of(params).map(p -> p.getClass())
@@ -355,6 +375,13 @@ public class CodeTester {
Object r = invokeMethod(invocationMsg, m, o, params);
+ if (r == null && !acceptNull) {
+ throw new BaseTester.FailedTestException(
+ expandMsg(invocationMsg) + "\n\n" +
+ "The method call returned null but a non-null value was expected."
+ );
+ }
+
recordCall(r, o, m, params);
return r;
@@ -373,13 +400,27 @@ public class CodeTester {
throw new BaseTester.FailedTestException(expandMsg(msg));
}
+
/**
* Convenience for callMsg with default messages.
+ *
+ * Will allow method to return null.
*/
public Object call(Object o,
String methodName,
Object... params) throws
BaseTester.FailedTestException {
+ return callAcceptNull(true, o, methodName, params);
+ }
+
+ /**
+ * Convenience for callMsgAcceptNull with default messages.
+ */
+ public Object callAcceptNull(boolean acceptNull,
+ Object o,
+ String methodName,
+ Object... params) throws
+ BaseTester.FailedTestException {
String base;
if (getLines().size() > 0) {
@@ -394,7 +435,30 @@ public class CodeTester {
String msg = base + "could not be made.";
String invokeMsg = base + "went wrong.";
- return callMsg(msg, invokeMsg, o, methodName, params);
+ return callMsgAcceptNull(msg,
+ invokeMsg,
+ acceptNull,
+ o,
+ methodName,
+ params);
+ }
+
+
+ /**
+ * Convenience for callStaticMsgAcceptNull with acceptNull as true
+ */
+ public Object callStaticMsg(String msg,
+ String invocationMsg,
+ Class<?> klass,
+ String methodName,
+ Object... params) throws
+ BaseTester.FailedTestException {
+ return callStaticMsgAcceptNull(msg,
+ invocationMsg,
+ true,
+ klass,
+ methodName,
+ params);
}
/**
@@ -404,19 +468,23 @@ public class CodeTester {
* msg and invocationMsg can contain LOG_EXPAND which will be replaced by
* getIndentedLinesString in the exception.
*
+ * Can specify whether a null return value is an error.
+ *
* @param msg the failure message
* @param invocationMsg failure message prefix in case method call
* throws exception (student code fails)
+ * @param acceptNull whether null is an ok return value
* @param klass the class having the method
* @param String name method name
* @param parameterTypes the arguments
* @return the result object
*/
- public Object callStaticMsg(String msg,
- String invocationMsg,
- Class<?> klass,
- String methodName,
- Object... params) throws
+ public Object callStaticMsgAcceptNull(String msg,
+ String invocationMsg,
+ boolean acceptNull,
+ Class<?> klass,
+ String methodName,
+ Object... params) throws
BaseTester.FailedTestException {
Class<?>[] parameterTypes
= Stream.of(params).map(p -> p.getClass())
@@ -433,6 +501,13 @@ public class CodeTester {
Object r = invokeMethod(invocationMsg, m, null, params);
+ if (r == null && !acceptNull) {
+ throw new BaseTester.FailedTestException(
+ expandMsg(invocationMsg) + "\n\n" +
+ "The method call returned null but a non-null value was expected."
+ );
+ }
+
recordStaticCall(r, klass, m, params);
return r;
@@ -443,21 +518,40 @@ public class CodeTester {
Utils.makeThrowableMsg(e.getCause())
);
}
+ catch (BaseTester.FailedTestException e) {
+ throw e;
+ }
catch (Throwable e) {
/* fall through */
+ System.out.println(e);
}
// failures fall through here
throw new BaseTester.FailedTestException(expandMsg(msg));
}
+
/**
- * Convenience for callMsg with default messages.
+ * Convenience for callMsgAcceptNull with acceptNull as true
*/
public Object callStatic(Class<?> klass,
String methodName,
Object... params) throws
BaseTester.FailedTestException {
+ return callStaticAcceptNull(true,
+ klass,
+ methodName,
+ params);
+ }
+
+ /**
+ * Convenience for callStaticMsgAcceptNull with default messages.
+ */
+ public Object callStaticAcceptNull(boolean acceptNull,
+ Class<?> klass,
+ String methodName,
+ Object... params) throws
+ BaseTester.FailedTestException {
String base;
if (getLines().size() > 0) {
@@ -472,10 +566,14 @@ public class CodeTester {
String msg = base + "could not be made.";
String invokeMsg = base + "went wrong.";
- return callStaticMsg(msg, invokeMsg, klass, methodName, params);
+ return callStaticMsgAcceptNull(msg,
+ invokeMsg,
+ acceptNull,
+ klass,
+ methodName,
+ params);
}
-
/**
* If a name is recorded for the object, return it, else null
*/
@@ -483,7 +581,6 @@ public class CodeTester {
return objectNames.get(System.identityHashCode(o));
}
-
/**
* Expand a string with log and arguments.
*
diff --git a/src/test/java/uk/ac/rhul/cs/javatester/UnitTests.java b/src/test/java/uk/ac/rhul/cs/javatester/UnitTests.java
index 34e0db3..a05098f 100644
--- a/src/test/java/uk/ac/rhul/cs/javatester/UnitTests.java
+++ b/src/test/java/uk/ac/rhul/cs/javatester/UnitTests.java
@@ -315,4 +315,34 @@ public class UnitTests {
};
assertFalse(tester.runTests());
}
+
+ @Test
+ public void testCallMethodNoNull() {
+ BaseTester tester = new BaseTester(NULL_PTR_CLASS) {
+ @SuppressWarnings("unused")
+ public boolean testCallMethod()
+ throws BaseTester.FailedTestException {
+ CodeTester ct = new CodeTester();
+ Object o = ct.construct(NULL_PTR_CLASS);
+ ct.callAcceptNull(false, o, "getNull");
+ return true;
+ }
+ };
+ assertFalse(tester.runTests());
+ }
+
+ @Test
+ public void testCallMethodStaticNoNull() {
+ BaseTester tester = new BaseTester(NULL_PTR_CLASS) {
+ @SuppressWarnings("unused")
+ public boolean testCallMethod()
+ throws BaseTester.FailedTestException {
+ CodeTester ct = new CodeTester();
+ Class<?> klass = ct.loadClass(NULL_PTR_CLASS);
+ ct.callStaticAcceptNull(false, klass, "getNull");
+ return true;
+ }
+ };
+ assertFalse(tester.runTests());
+ }
}
diff --git a/src/test/java/uk/ac/rhul/cs/javatester/solution/NullPtrMethod.java b/src/test/java/uk/ac/rhul/cs/javatester/solution/NullPtrMethod.java
index 1788f9f..6ecdff3 100644
--- a/src/test/java/uk/ac/rhul/cs/javatester/solution/NullPtrMethod.java
+++ b/src/test/java/uk/ac/rhul/cs/javatester/solution/NullPtrMethod.java
@@ -16,4 +16,8 @@ public class NullPtrMethod {
String n = null;
n.length();
}
+
+ public static String getNull() {
+ return null;
+ }
}
--
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