Bloodhound (randoop 4.3.4 API)

java.lang.Object
- randoop.generation.Bloodhound

All Implemented Interfaces:

TypedOperationSelector
```
public class Bloodhound
extends java.lang.Object
implements TypedOperationSelector
```
Implements the Bloodhound component, as described by the paper "GRT: Program-Analysis-Guided Random Testing" by Ma et. al (appears in ASE 2015): https://people.kth.se/~artho/papers/lei-ase2015.pdf .
Bloodhound computes a weight for each method under test by taking a weighted combination of
- the uncovered branch ratio and
- the ratio between the number of times the method has been successfully invoked (to be the last statement of a new regression test) and the maximum number of times any method under test has been successfully invoked.
A method is "successfully invoked" when a method under test is used to create a new sequence and the sequence is kept as a regression test. An alternative definition of "successful invocations" is the total number of times the method appears in any regression test. Both definitions are consistent with the description in the GRT paper. We believe our implementation, which uses the first definition, is likely what was intended by the authors of the GRT paper.

Field Summary

Fields
Modifier and Type	Field and Description
`private static double`	`alpha` Parameter for balancing branch coverage and number of times a method was chosen.
`private static int`	`branchCoverageInterval` Branch coverage is recomputed after this many successful invocations (= this many new tests were generated).
`private CoverageTracker`	`coverageTracker` Coverage tracker used to get branch coverage information of methods under test.
`private long`	`lastUpdateTime` `System.currentTimeMillis()` when branch coverage was last updated.
`private int`	`maxSuccM` Maximum number of times any method under test has been successfully invoked.
`private java.util.Map<TypedOperation,java.lang.Integer>`	`methodInvocationCounts` Map from methods under test to the total number of times they have ever been successfully invoked by the `AbstractGenerator`.
`private java.util.Map<TypedOperation,java.lang.Integer>`	`methodSelectionCounts` Map from methods under test to the number of times they have been recently selected by the `ForwardGenerator` to construct a new sequence.
`private java.util.Map<TypedOperation,java.lang.Double>`	`methodWeights` Map from methods under test to their weights.
`private SimpleArrayList<TypedOperation>`	`operationSimpleList` List of operations, identical to `ForwardGenerator`'s operation list.
`private static double`	`p` Parameter for decreasing weights of methods between updates to coverage information.
`private static long`	`t` Time interval, in milliseconds, at which to recompute weights.
`private int`	`totalSuccessfulInvocations` The total number of successful invocations of all the methods under test.
`private double`	`totalWeightOfMethodsUnderTest` The total weight of all the methods that are under test.

Constructor Summary

Constructors
Constructor and Description

Bloodhound(java.util.List<TypedOperation> operations, java.util.Set<ClassOrInterfaceType> classesUnderTest)
Initialize Bloodhound.

Constructors
Constructor and Description
`Bloodhound(java.util.List<TypedOperation> operations, java.util.Set<ClassOrInterfaceType> classesUnderTest)` Initialize Bloodhound.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`incrementSuccessfulInvocationCount(TypedOperation operation)` Increments the number of times a method under test was successfully invoked.
`private void`	`logMethodWeights()` For debugging, print all method weights to standard output.
`void`	`newRegressionTestHook(Sequence sequence)` Increment the number of successful invocations of the last method in the newly-created sequence that was classified as a regression test.
`TypedOperation`	`selectOperation()` Selects a method under test for the `ForwardGenerator` to use to construct a new sequence.
`private void`	`updateBranchCoverageMaybe()` When an interval is reached, the branch coverage information for all methods under test is updated and the weight for every method under test is recomputed.
`private double`	`updateWeight(TypedOperation operation)` Recompute weight for a method under test.
`private void`	`updateWeightsForAllOperations()` Computes and updates weights in `methodWeights` map for all methods under test.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - coverageTracker
```
private final CoverageTracker coverageTracker
```
    Coverage tracker used to get branch coverage information of methods under test.
  - methodWeights
```
private final java.util.Map<TypedOperation,java.lang.Double> methodWeights
```
    Map from methods under test to their weights. These weights are dynamic and depend on branch coverage.
  - methodSelectionCounts
```
private final java.util.Map<TypedOperation,java.lang.Integer> methodSelectionCounts
```
    Map from methods under test to the number of times they have been recently selected by the ForwardGenerator to construct a new sequence. This map is cleared every time branch coverage is recomputed.
  - methodInvocationCounts
```
private final java.util.Map<TypedOperation,java.lang.Integer> methodInvocationCounts
```
    Map from methods under test to the total number of times they have ever been successfully invoked by the AbstractGenerator. The integer value for a given method is non-decreasing during a run of Randoop.
  - operationSimpleList
```
private final SimpleArrayList<TypedOperation> operationSimpleList
```
    List of operations, identical to ForwardGenerator's operation list. Used for making random, weighted selections for a method under test.
  - alpha
```
private static final double alpha
```
    Parameter for balancing branch coverage and number of times a method was chosen. The name "alpha" and the specified value are both from the GRT paper.
    
    See Also:
    
    Constant Field Values
  - p
```
private static final double p
```
    Parameter for decreasing weights of methods between updates to coverage information. The name "p" and the specified value are both from the GRT paper.
    
    See Also:
    
    Constant Field Values
  - t
```
private static final long t
```
    Time interval, in milliseconds, at which to recompute weights. The name "t" and the specified value are both from the GRT paper.
    
    See Also:
    
    Constant Field Values
  - lastUpdateTime
```
private long lastUpdateTime
```
    System.currentTimeMillis() when branch coverage was last updated.
  - branchCoverageInterval
```
private static final int branchCoverageInterval
```
    Branch coverage is recomputed after this many successful invocations (= this many new tests were generated).
    
    See Also:
    
    Constant Field Values
  - totalSuccessfulInvocations
```
private int totalSuccessfulInvocations
```
    The total number of successful invocations of all the methods under test.
  - maxSuccM
```
private int maxSuccM
```
    Maximum number of times any method under test has been successfully invoked. This value is initialized to 1 because it is used as the denominator of a division in computing a method's weight. The name is from the GRT paper, which calls this quantity "maxSucc(M)".
  - totalWeightOfMethodsUnderTest
```
private double totalWeightOfMethodsUnderTest
```
    The total weight of all the methods that are under test. This is used by Randomness to randomly select an element from a list of weighted elements.
- Constructor Detail
  - Bloodhound
```
public Bloodhound(java.util.List<TypedOperation> operations,
                  java.util.Set<ClassOrInterfaceType> classesUnderTest)
```
    Initialize Bloodhound. Branch coverage information is initialized and all methods under test are assigned a weight based on the weighting scheme defined by GRT's description of Bloodhound.
    
    Parameters:
    
    operations - list of operations under test
    
    classesUnderTest - set of classes under test
- Method Detail
  - selectOperation
```
public TypedOperation selectOperation()
```
    Selects a method under test for the ForwardGenerator to use to construct a new sequence. A method under test is randomly selected with a weighted probability.
    
    Specified by:
    
    selectOperation in interface TypedOperationSelector
    
    Returns:
    
    the chosen TypedOperation for the new sequence
  - updateBranchCoverageMaybe
```
private void updateBranchCoverageMaybe()
```
    When an interval is reached, the branch coverage information for all methods under test is updated and the weight for every method under test is recomputed.
    There are two choices for when to update branch coverage information:
    - Time: branch coverage is updated when more than t milliseconds have elapsed since branch coverage was last updated. This is GRT's approach and is the default. It makes Randoop non-deterministic.
    - Count of successful invocations: branch coverage is updated after every branchCoverageInteral successful invocations (of any method under test).
  - logMethodWeights
```
private void logMethodWeights()
```
    For debugging, print all method weights to standard output.
  - updateWeightsForAllOperations
```
private void updateWeightsForAllOperations()
```
    Computes and updates weights in methodWeights map for all methods under test. Recomputes the totalWeightOfMethodsUnderTest to avoid problems with round-off error.
  - updateWeight
```
private double updateWeight(TypedOperation operation)
```
    Recompute weight for a method under test. A method under test is assigned a weight based on a weighted combination of
    - the number of branches uncovered and
    - the ratio between the number of times this method has been recently selected and the maximum number of times any method under test has been successfully invoked.
    The weighting scheme is based on Bloodhound in the Guided Random Testing (GRT) paper.
    Parameters:
    
    operation - method to compute weight for
    
    Returns:
    
    the updated weight for the given operation
  - incrementSuccessfulInvocationCount
```
public void incrementSuccessfulInvocationCount(TypedOperation operation)
```
    Increments the number of times a method under test was successfully invoked.
    
    Parameters:
    
    operation - the method under test that was successfully invoked
  - newRegressionTestHook
```
public void newRegressionTestHook(Sequence sequence)
```
    Increment the number of successful invocations of the last method in the newly-created sequence that was classified as a regression test.
    
    Specified by:
    
    newRegressionTestHook in interface TypedOperationSelector
    
    Parameters:
    
    sequence - newly-created sequence that was classified as a regression test

Class Bloodhound

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

coverageTracker

methodWeights

methodSelectionCounts

methodInvocationCounts

operationSimpleList

alpha

p

t

lastUpdateTime

branchCoverageInterval

totalSuccessfulInvocations

maxSuccM

totalWeightOfMethodsUnderTest

Constructor Detail

Bloodhound

Method Detail

selectOperation

updateBranchCoverageMaybe

logMethodWeights

updateWeightsForAllOperations

updateWeight

incrementSuccessfulInvocationCount

newRegressionTestHook