public IEnumerable<Violation> Apply(TestCase testCase)
{
var calledAssertingMethods = testCase.GetCalledAssertingMethods();
var tracker = new MethodValueTracker(testCase.TestMethod);
// For each asserting method with >= 1 parameters:
foreach (var cm in calledAssertingMethods)
{
var methodRef = cm.MethodReference;
var parameterPurposes = testCase.Framework.GetParameterPurposes(methodRef);
if (!IsSingleTruthCheckingMethod(methodRef, parameterPurposes))
continue;
foreach (var valueGraph in tracker.ValueGraphs)
{
IList<MethodValueTracker.Value> consumedValues =
tracker.GetConsumedValues(valueGraph, cm.Instruction).ToList();
if (consumedValues.Count == 0)
continue; // not part of value graph
var interestingValue = consumedValues[0];
var producers = UltimateProducers(interestingValue);
if (producers.Count > 1)
{
yield return new Violation(this, testCase, cm.Instruction, string.Format("{0}.{1} performs a boolean test on a composite boolean value",
cm.MethodReference.DeclaringType.Name,
cm.MethodReference.Name));
}
}
}
}
public void TestThatValueConsumptionForInstructionMatchesPath()
{
var method = GetType().FindMethod("MethodWithBranch()");
var tracker = new MethodValueTracker(method);
var graph = tracker.ValueGraphs[1]; // second path
// Find the last instruction that stores to y (first local)
var instr = method.Body.Instructions.Where(i => i.OpCode == OpCodes.Stloc_0).Last();
var producers = tracker.GetConsumedValues(graph, instr).Select(v => v.Producer.OpCode).ToList();
// Expect the producer of the conssumed value to load from u (third local)
CollectionAssert.AreEqual(new[] { OpCodes.Ldloc_2 }, producers);
}
private ICollection<Instruction> UltimateProducers(MethodValueTracker.Value v)
{
// We track backwards and record values without parents. The producers of
// those values are considered the ultimate producers of the given value.
var result = new List<Instruction>();
var values = new Queue<MethodValueTracker.Value>();
values.Enqueue(v);
while (values.Count > 0)
{
var aValue = values.Dequeue();
if (aValue.Parents.Count == 0)
{
result.Add(aValue.Producer);
continue;
}
foreach (var parent in aValue.Parents)
{
values.Enqueue(parent);
}
}
return result;
}
private IEnumerable<OpCode> FindAllSourceValueOpCodes(MethodValueTracker tracker, Instruction instruction)
{
var consumedValues = tracker.GetConsumedValues(tracker.ValueGraphs[0], instruction);
var sourceValues = consumedValues.SelectMany(tracker.FindSourceValues);
return sourceValues.Select(v => v.Producer.OpCode).Distinct();
}
public void TestThatTrackerExposesTwoValueGraphsForMethodWithTwoPaths()
{
var method = GetType().FindMethod("MethodWithBranch()");
var tracker = new MethodValueTracker(method);
Assert.AreEqual(2, tracker.ValueGraphs.Count);
}
private bool IsProducedByUnapprovedCall(MethodValueTracker.Value value)
{
var i = value.Producer;
if (i.OpCode.FlowControl != FlowControl.Call)
return false;
var calledMethod = i.Operand as MethodReference;
if (calledMethod.IsConstructor())
return false; // constructing an object locally is ok
var propertyDef = TryGetPropertyDefForPropertyGetter(calledMethod);
if (propertyDef != null && IsStaticGetOnlyProperty(propertyDef))
return false;
if (IsDataConversionCall(calledMethod))
return false;
if (_framework.IsDataAccessorMethod(calledMethod))
return false;
if (IsGeneratedByTypeOf(value))
return false;
return true;
}
private bool HasForbiddenProducer(MethodValueTracker.Value value, IList<FieldDefinition> whitelistedFields)
{
var producer = value.Producer;
if (IsProducedByUnapprovedCall(value) || (IsFieldLoad(producer, whitelistedFields) && !IsStaticReadonlyFieldLoad(producer)))
return true;
return false;
}
private static bool IsProducedByDoubleCilComparison(MethodValueTracker.Value value, out MethodValueTracker.Value originalComparisonOutcome)
{
// Assumption: The instruction is a binary comparison.
originalComparisonOutcome = null;
var parents = value.Parents.ToList();
var producer = value.Producer;
if (producer.OpCode != OpCodes.Ceq)
return false; // lte/gte/neq = cgt/clt/ceq followed by ceq
var ldc0 = parents.Where(v => v.Producer.OpCode == OpCodes.Ldc_I4_0).FirstOrDefault();
if (ldc0 == null)
return false; // one of the ceq operands should've been produced by ldc.i4.0
var other = parents[1 - parents.IndexOf(ldc0)];
if (!IsBinaryComparison(other.Producer))
return false; // the other operand should've been produced by a binary comparison
originalComparisonOutcome = other;
return true; // match!
}
public void TestThatQueryInstructionCannotBeNull()
{
var method = GetType().FindMethod("DirectConstantUseByStaticMethod()");
var tracker = new MethodValueTracker(method);
tracker.GetConsumedValues(tracker.ValueGraphs[0], null);
}
public void TestThatObjectConstructionIsHandled()
{
var method = GetType().FindMethod("ObjectConstruction()");
var tracker = new MethodValueTracker(method);
var opCodes = FindAllSourceValueOpCodes(tracker, LastCall(method));
CollectionAssert.AreEquivalent(new[] { OpCodes.Newobj }, opCodes);
}
public void TestThatGraphCannotBeNullWhenQueryingConsumedValues()
{
var method = GetType().FindMethod("DirectConstantUseByStaticMethod()");
var tracker = new MethodValueTracker(method);
tracker.GetConsumedValues(null, LastCall(method));
}
public void TestThatConsumedValuesIncludesFirstArgOfStaticCallInStatic()
{
var method = GetType().FindMethod("StaticMethodWithStaticCall(System.Int32)");
var tracker = new MethodValueTracker(method);
var consumedValues = tracker.GetConsumedValues(tracker.ValueGraphs[0], LastCall(method));
var opCodes = consumedValues.Select(v => v.Producer.OpCode);
// Ldarg_0 should be in the list!
CollectionAssert.AreEqual(new[] { OpCodes.Ldarg_0 }, opCodes);
}
public void TestThatConsumedValuesExcludesThisObjectForVirtualCall()
{
var method = GetType().FindMethod("DirectConstantUseByVirtualMethod()");
var tracker = new MethodValueTracker(method);
var consumedValues = tracker.GetConsumedValues(tracker.ValueGraphs[0], LastCall(method));
var opCodes = consumedValues.Select(v => v.Producer.OpCode);
// Ldarg_0 should not be in the list!
CollectionAssert.AreEqual(new[] { OpCodes.Ldc_I4_S }, opCodes);
}
public void TestThatConsumedValuesAreEmptyWhenQueryInstructionIsNotPartOfMethod()
{
var method = GetType().FindMethod("DirectConstantUseByStaticMethod()");
var method2 = GetType().FindMethod("DirectConstantUseByVirtualMethod()");
var tracker = new MethodValueTracker(method);
var values = tracker.GetConsumedValues(tracker.ValueGraphs[0], LastCall(method2));
Assert.AreEqual(0, values.Count());
}
public void TestThatConsumedValueCountCorrespondsToActualConsumption()
{
var method = GetType().FindMethod("DirectConstantUseByStaticMethod()");
var tracker = new MethodValueTracker(method);
var consumedValues = tracker.GetConsumedValues(tracker.ValueGraphs[0], LastCall(method));
Assert.AreEqual(1, consumedValues.Count());
}
public void TestThatConstantConsumedViaBoxedValueIsFound()
{
var method = GetType().FindMethod("BoxedConstantUseByStaticMethod()");
var tracker = new MethodValueTracker(method);
var consumedValue = tracker.GetConsumedValues(tracker.ValueGraphs[0], LastCall(method)).First();
var roots = tracker.FindSourceValues(consumedValue);
Assert.AreEqual(OpCodes.Ldc_I4_S, roots.First().Producer.OpCode);
}
private static bool IsProducedByBinaryComparison(MethodValueTracker.Value value, out IList<MethodValueTracker.Value> operands)
{
var producer = value.Producer;
if (IsBinaryComparison(producer))
{
// Note: <=, => and != result in cgt, lgt and ceq, respectively, followed by
// ceq with one operand being 0 (so produced by ldc.i4.0). Therefore, to handle
// these comparisons, we need to backtrack one value in this particular case.
MethodValueTracker.Value originalComparisonOutcome;
if (IsProducedByDoubleCilComparison(value, out originalComparisonOutcome))
{
// Backtrack to the value produced by the comparison behind ceq!
value = originalComparisonOutcome;
}
operands = value.Parents.ToList();
return true;
}
operands = null;
return false;
}
public void TestThatSourceValueIsTrackedThroughRefManipulation()
{
var method = GetType().FindMethod("UseOfValueManipulatedAsReference()");
var tracker = new MethodValueTracker(method);
var opCodes = FindAllSourceValueOpCodes(tracker, LastCall(method));
CollectionAssert.AreEquivalent(new[] { OpCodes.Ldc_I4_4, OpCodes.Ldc_I4_5 }, opCodes);
}
private Instruction FirstForbiddenProducer(Graph<MethodValueTracker.Value> valueGraph, MethodValueTracker.Value v, IList<FieldDefinition> whitelistedFields)
{
return valueGraph.Walk(v).Where(val => HasForbiddenProducer(val, whitelistedFields)).Select(value => value.Producer).FirstOrDefault();
}
public void TestThatSourceValueIsTrackedThroughReturnValue()
{
var method = GetType().FindMethod("UseOfReturnValue()");
var tracker = new MethodValueTracker(method);
var opCodes = FindAllSourceValueOpCodes(tracker, LastCall(method));
CollectionAssert.AreEquivalent(new[] { OpCodes.Ldc_I4_5, OpCodes.Ldc_I4_6 }, opCodes);
}
private bool IsGeneratedByTypeOf(MethodValueTracker.Value value)
{
var i = value.Producer;
var calledMethod = i.Operand as MethodReference;
// typeof(X) generates a call to System.Type::GetTypeFromHandle, which can be manually
// called as well. Check if its argument is placed on the stack through ldtoken, in
// which case we assume it wasn't.
if (!GetTypeFromHandleSignature.Equals(calledMethod.FullName))
return false;
var parent = value.Parents.FirstOrDefault();
if (parent == null)
return false;
var parentProducer = parent.Producer;
return parentProducer.OpCode == OpCodes.Ldtoken;
}
public void TestThatSourceValueIsTrackedThroughtOutValueDespitePreviousUseOfOutVariable()
{
var method = GetType().FindMethod("UseOfOutValueTwice()");
var tracker = new MethodValueTracker(method);
var opCodes = FindAllSourceValueOpCodes(tracker, LastCall(method));
CollectionAssert.AreEquivalent(new[] { OpCodes.Ldc_I4_1, OpCodes.Ldc_I4_2 }, opCodes);
}
public IEnumerable<Violation> Apply(TestCase testCase)
{
// Store the framework so that we don't have to pass it around everywhere.
_framework = testCase.Framework;
var calledAssertingMethods = testCase.GetCalledAssertingMethods();
var tracker = new MethodValueTracker(testCase.TestMethod);
var whitelistedFields = FindWhitelistedFields(testCase.TestMethod.DeclaringType);
// For each asserting method with >= 1 parameters:
foreach (var cm in calledAssertingMethods.Where(cm => cm.MethodDefinition.HasParameters))
{
var method = cm.MethodDefinition;
//TODO: if the method is a helper, we need to "unfold" the helper
// to get to the real asserting methods, and this will require us
// to join value-generation graphs across method calls...
var paramPurposes = _framework.GetParameterPurposes(method);
if (paramPurposes == null) continue; // unknown method, rule does not apply
foreach (var valueGraph in tracker.ValueGraphs)
{
IList<MethodValueTracker.Value> consumedValues = tracker.GetConsumedValues(valueGraph, cm.Instruction).ToList();
if (consumedValues.Count == 0)
continue; // not part of value graph
// Build a list of arguments with the details we need to know if the rule applies.
var arguments = method.Parameters
.Select((p, index) => new ArgumentDetails { Method = method, Index = index, Purpose = paramPurposes[index], ConsumedValue = consumedValues[index] }).ToList();
// Handle cases like Assert.IsTrue(x == 5) by expanding arguments
ExpandIfSingleTruthCheckingMethod(method, ref arguments);
// We're only interested in arguments that represent expectations!
var interestingArguments = arguments.Where(a => IsPerhapsExpectation(a.Purpose)).ToList();
// This might happen with for example Assert.Fail("some reason").
if (interestingArguments.Count == 0)
continue;
// Add in the "forbidden producer", if any, for each argument. A forbidden producer is an
// instruction that generates a value externally, such as a call.
interestingArguments = interestingArguments.Select(
a => { a.ForbiddenProducer = FirstForbiddenProducer(valueGraph, a.ConsumedValue, whitelistedFields); return a; }).ToList();
// If there is at least one locally produced argument, the rule doesn't apply.
if (interestingArguments.Any(IsLocallyProduced))
continue;
if (interestingArguments.All(a => a.Purpose == ParameterPurpose.ExpectedOrActual))
{
// Since we don't know exactly which parameter that represents the expectation, we
// just generate a single violation.
yield return new Violation(this, testCase, interestingArguments[0].ConsumedValue.Consumer,
CreateViolationMessageForUncertainCase(interestingArguments[0]));
continue;
}
foreach (var a in interestingArguments.Where(IsExternallyProduced))
{
// Generate a violation at the location of the forbidden producer!
yield return new Violation(this, testCase, a.ForbiddenProducer, CreateViolationMessage(a));
}
}
}
}
public void TestThatSourceValuesAreFoundThroughSequenceOfCalculations()
{
var method = GetType().FindMethod("CalculatedValueUseByStaticMethod(System.Int32,System.Int32)");
var tracker = new MethodValueTracker(method);
var opCodes = FindAllSourceValueOpCodes(tracker, LastCall(method));
CollectionAssert.AreEquivalent(new[] { OpCodes.Ldarg_1, OpCodes.Ldarg_2, OpCodes.Ldc_I4_1 }, opCodes);
}
public void TestThatTrackerExposesValueGraphsForAllCasesOfSwitchStatement()
{
var method = GetType().FindMethod("MethodWithSwitch()");
var tracker = new MethodValueTracker(method);
Assert.AreEqual(3, tracker.ValueGraphs.Count);
}
private static void PrintNode(StringBuilder builder, MethodValueTracker.Value node, int indent)
{
builder.Append("".PadRight(indent * 2));
PrintValue(builder, node);
foreach (var parent in node.Parents)
{
PrintNode(builder, parent, indent + 1);
}
}
public void TestThatValueConsumptionForInstructionOutsidePathIsEmpty()
{
var method = GetType().FindMethod("MethodWithBranch()");
var tracker = new MethodValueTracker(method);
var graph = tracker.ValueGraphs[0]; // first path
// Find the last instruction that stores to y, part of second path
var instr = method.Body.Instructions.Where(i => i.OpCode == OpCodes.Stloc_0).Last();
var consumed = tracker.GetConsumedValues(graph, instr);
Assert.AreEqual(0, consumed.Count());
}
private static void PrintValue(StringBuilder builder, MethodValueTracker.Value node)
{
builder.AppendFormat("Value produced by {0} and consumed by {1} [#parents={2}].\n",
InstructionToString(node.Producer), InstructionToString(node.Consumer),
node.Parents.Count);
}
