Dear QVTo
developers,
Our team is developing with QVTo tool, and
we found a bug while running with QVTo Junit test. After
spending some time to find the reason behind, we fixed it.
Hereunder please find the problem, the fixed file, and the
analysis.
Problem
After building the QVTo source code, we ran
the Junit test with following command line:
junit
--launch
"org.eclipse.m2m.tests.qvt.oml/org.eclipse.m2m.tests.qvt.oml.AllTests.launch"
--flatXML --output "${WORKSPACE}/MMT-QVTo.test.results/org.eclipse.m2m.tests.qvt.oml.AllTests.xml"
Occasionally, we got the following failure.
One of the Junit tests aims to test for the stack overflow,
and it failed with an assertion. It is noticeable to see that
the failure is not happened all the time. Sometime it passed,
while sometime it failed.
INFO:
Running test
org.eclipse.m2m.tests.qvt.oml.transform.TestStackTrace.testMappingCallInProperty...
INFO:
...OK [0,202s]
INFO:
Running test
org.eclipse.m2m.tests.qvt.oml.transform.TestStackTrace.testStackOverFlow...
INFO:
...Failure [0,188s]
WARN:
junit.framework.AssertionFailedError: expected:<6> but
was:<5>
at junit.framework.Assert.fail(Assert.java:57)
at junit.framework.Assert.failNotEquals(Assert.java:329)
at junit.framework.Assert.assertEquals(Assert.java:78)
at junit.framework.Assert.assertEquals(Assert.java:234)
at junit.framework.Assert.assertEquals(Assert.java:241)
Fixed File
${WORKSPACE}/org.eclipse.m2m.tests.qvt.oml/src/org/eclipse/m2m/tests/qvt/oml/transform/TestStackTrace.java,
line 92:
85
for
(QVTStackTraceElement element
:
e.getQvtStackTrace())
{
86
if(--elementCount
== 0) {
87
break;
88
}
89
assertEquals("causeStackOverFlow",
element.getOperationName());
//$NON-NLS-1$
90
assertEquals("auxtransf",
element.getModuleName());
//$NON-NLS-1$
91
assertEquals("auxtransf.qvto",
element.getUnitName());
//$NON-NLS-1$
92
//assertEquals(6,
element.getLineNumber());
93
assertTrue((5 == element.getLineNumber())
|| (6 ==
element.getLineNumber()));
94
}
We made a comment of line 92, and added one
line below in line 93. Instead of only checking line number 5,
both line number 5 and 6 are acceptable.
Analysis
The test code here wants to test for the
stack overflow, with
causeStackOverFlow method
in auxtransf.qvto file. If we look inside this qvto file, we
may find:
1
modeltype ecore uses
'http://www.eclipse.org/emf/2002/Ecore';
2
3
transformation auxtransf(in inModel : ecore, out outModel :
ecore);
4
5
query causeStackOverFlow() : OclAny {
6
causeStackOverFlow(); -- line 7: causing stack overflow
7
}
The method causeStackOverFlow called itself
here, the stack will be finally overflow because each call
will push method related data into the stack. When the stack
is full, an exception will be thrown.
The author of this piece of code might
return the line number, and line 6 is the expected value. But
the line sequence of this call should be: 5, 6, 5, 6, 5, 6, …,
instead of 6, 6, 6, …. Because the entrance of this call is
line 5, which might be neglected by the author. This is also
the reason why the test failure shows occasionally. When the
exception failed in line 6, it passed. When the exception
failed in line 5, it failed.
We recommend to fix this bug, in order to
avoid any further problem by the other developers.
Best
wishes,
Jiazhuo Zhang
