JP6888336B2 - Stub generators, methods, and programs - Google Patents

Description

The disclosed technique relates to a stub generator, a stub generator, and a stub generator.

In the program testing technology by symbolic execution, when a test case is generated, a driver that builds and sets the test environment and a stub that is a dummy implementation of the program parts called by the program to be tested are prepared. There is.

For example, a system equipped with a module execution means that executes a module to be tested, a dependent module called from the module, and a stub that substitutes for the behavior of the procedure performed by the dependent module according to the description contents of each. Proposed. This module execution means detects a call from the module under test to the dependent module, determines whether the module to execute the processing of the call is the dependent module or the stub according to a predetermined condition, and executes the processing of the call according to the determination. Includes processing delegation means to make.

In addition, an information processing device that inputs the target program and the path information on the target program and generates a stub program that represents the change according to the path information of the variable value updated by the external program called from the target program is proposed. Has been done. This device generates a test target program in which a call to an external program in the target program is replaced with a call to a stub program, and generates a driver program that calls the test target program using the initial value of the path information.

JP-A-2009-129133 Japanese Unexamined Patent Publication No. 2012-181666

In the target program where the inheritance relationship between the classes included in the target program is defined, when assigning an object to a certain variable, it is necessary to type-convert the object to an appropriate class.

However, depending on the inheritance relationship between the type of the object returned from the stub and the type of the return destination class, an error may occur when the target program accesses the returned object. In this case, the execution of the test of the target program is interrupted at that point, and the test coverage is lowered.

One aspect of the disclosed technique is to generate stubs that reduce test completeness in symbolic execution of the program under test, including type conversion of objects.

In one aspect of the disclosed technique, the first generation unit stubs a class called from a method included in a program under test and generates a first stub that returns a dummy object. When the object returned from the first stub generated by the first generation unit is converted by the second generation unit at the return destination, the object is returned at the return destination based on the first stub. Generate a second stub that returns an object that can be type converted. In the test target program, the update unit updates the target of the class in which the returned object is type-converted at the return destination from the first stub to the second stub generated based on the first stub. ..

One aspect is that it is possible to generate a stub that suppresses a decrease in test completeness in symbolic execution of a program under test including type conversion of an object.

It is a functional block diagram of the stub generator which concerns on this embodiment. It is a figure for demonstrating the procedure of the unit test of a program using a symbolic execution technique. It is a figure which shows an example of the default value for each return type of a method of a primitive type. It is a figure for demonstrating the stub generation when the return type is a primitive. It is a figure for demonstrating the stub generation when the return type is a user-specified type object. It is a figure for demonstrating the exception occurrence by downcast. It is a block diagram which shows the outline of the computer which functions as the stub generation apparatus which concerns on this embodiment. It is a flowchart which shows an example of the stub generation processing in this embodiment. It is a figure which shows the inheritance relationship between a class in a test subject class. It is a figure which shows an example of the test subject class. It is a figure for demonstrating the generation of an original stub. It is a figure for demonstrating the statement including a class cast. It is a figure which shows an example of a cast set. It is a figure for demonstrating the generation of a derivative stub. It is a figure which shows an example of the update of the stub class name in the test subject class. It is a figure which shows the call of a stub from a class under test. It is a figure for demonstrating the case which calls the original stub. It is a figure for demonstrating the case which calls a derived stub.

Hereinafter, an example of an embodiment relating to the disclosed technology will be described in detail with reference to the drawings. In this embodiment, a case where the program to be tested is a class and a method described in Java (registered trademark) will be described as an example.

As shown in FIG. 1, the stub generator 10 according to the present embodiment accepts the test target class 31 as an input. Then, the stub generator 10 generates and outputs a stub to be used in the unit test of the program using the symbolic execution technique.

Here, the procedure for unit testing a program using the symbolic execution technology will be described.

As shown in FIG. 2, first, a symbolic execution driver and a stub are generated (S100).

The symbolic execution driver is a program that builds and sets the execution environment of the test target class 31 and starts the test target class. The stub is a dummy implementation of the program component called by the test target class. The program component called from the test target class may be in the process of being implemented or the program component may not be tested at the test stage of the test target class. In addition, a program component may execute external access to a file, a database, or the like. For this reason, if the program component called from the test target class cannot be used at the time of testing, a stub is used instead of the actual program component.

Next, the generated symbolic execution driver and stub and the test target class are input to the symbolic execution engine 200, and a test case is generated by the symbolic execution engine 200 (S101). Then, by executing the test with the unit test tool 201 using the generated test case, the test result for the test target class can be obtained (S103).

Regarding the generation of stub, when the class is called from the method included in the test target class and the type of return value from the stub target class to each method (hereinafter referred to as "return type") is a primitive type. Think. In this case, without the implementation body, for example, as shown in FIG. 3, a stub that returns a predetermined default value according to the return type of the method is generated. For example, as shown in FIG. 4, the return type of method1 that calls the original class (StubSample) is "int", which is a primitive type. Using the example of FIG. 3, since the default value for the return type "int" is "0", a code for returning 0 ("return 0") is described in the body part of method1. Also, when the return type is "void" like method2 included in the original class (StubSimple), nothing is returned from the stub, so the body part is left empty. In this way, the original class is stubbed. That is, a stub is generated.

Also, regarding the generation of stubs, consider the case where the return type of the method that calls the class to be stubized is the user-specified type. For example, it is assumed that the return type "ClassA" of method1 that calls the class to be stubbed is a user-specified type as shown in FIG. In this case, when "null" is returned from the stub, a NullPointerException exception occurs at the point where the return value "Null" is accessed in the test target class. To avoid this exception, a stub is generated that returns an instance of a user-specified type of object. Default values are passed to each argument of the constructor.

Here, if an inheritance relationship is defined between each class called from the method included in the test target class, when assigning an object to a certain variable, it is necessary to cast (type conversion) to the appropriate class. .. In the case of Java (registered trademark), casting from child class to parent class (upcast) is possible, but casting from parent class to child class (downcast) is not possible. However, downcasting after upcasting is possible.

For example, there are the following patterns in the class cast when the child class "Child" inherits the parent class "Parent".

(1) Partent p = (Parent) newChild ();
(2) Partent p = (Parent) newChild ();
Child c = (Child) p;
(3) Child c = (Child) new Partent ();

The "new Child ()" in (1) above represents instantiation of an object of the child class "Child", and "(Parent)" represents casting the object to the parent class "Parent". Further, "Parent p =" indicates that an object is assigned to the variable p of the parent class "Parent". That is, the above (1) represents an upcast, and such a classcast is possible.

In (2) above, the instantiated child class "Child" object is cast to the parent class "Parent", and the cast object is cast to the child class "Child". That is, the above (2) represents a downcast after an upcast, and such a classcast is possible.

The above (3) represents downcasting the object of the instantiated parent class "Parent" to the child class "Child", and such a class cast is not possible.

Next, in the test target class, the problem that occurs when the object returned from the stub is class cast will be described.

As shown in FIG. 6, the object p upcast from the child class "Child" to the parent class "Parent" is returned from the original class called from the test target class. At the return destination, the object p of the parent class "Parent" is cast to the child class "Child". In this case, since it is a downcast after an upcast, a class cast is possible.

However, when this original class is stubized, as shown in FIG. 6, it is assumed that a stub for returning an instance of the return type "Parent" of method1 is generated. In this case, the return destination of the object is a downcast from the parent class "Parent" to the child class "Child", so a ClassCastException exception occurs.

Therefore, in the present embodiment, a stub that returns the object according to the class cast at the object return destination is generated. Hereinafter, each part of the stub generator 10 will be described in detail.

As shown in FIG. 1, the stub generation device 10 functionally includes a stub generation unit 11, an analysis unit 12, a derivative stub generation unit 13, and an update unit 14. The stub generation unit 11 is an example of the first generation unit of the disclosed technology, and the analysis unit 12 and the derivative stub generation unit 13 are examples of the second generation unit of the disclosure technology.

The stub generation unit 11 stubs the stubization target class called from the method included in the input test target class, and generates a stub to be called at the time of symbolic execution. As a method for generating stubs by the stub generation unit 11, a conventionally known method can be used, and therefore detailed description thereof will be omitted in the present embodiment.

The analysis unit 12 identifies a place where the object returned from the stub generated by the stub generation unit 11 is class cast at the return destination of the test target class.

Specifically, the analysis unit 12 collects the class names (hereinafter, referred to as “stub class names”) of the stubs (stubized classes) generated by the stub generation unit 11 and stores them in the stub set 21. Further, the analysis unit 12 calls the stub indicated by the stub class name stored in the stub set 21 from the test target class, and extracts all statements in which the object returned from the stub is cast. From each extracted statement, the analysis unit 12 acquires information on the class to which the object is cast, the stub class name of the stub to be called, and the method name of the method that calls the stub. The analysis unit 12 creates a record from the acquired information and stores it in the cast set 22.

The derived stub generation unit 13 generates a stub that returns an object corresponding to the cast destination class by deriving a stub that returns an object that is class cast at the return destination. Hereinafter, the stub generated by the derived stub generation unit 13 is referred to as a “derivative stub”.

Specifically, the derived stub generator 13 duplicates the stub code indicated by the stub class name included in each record stored in the cast set 22, and changes the stub class name to a name indicating that it is a derived stub. change. For example, the derived stub generation unit 13 can change the stub class name of the derived stub to a name obtained by adding "derivative i" after the stub class name of the original stub. i can be an integer that counts up from 0 each time a derived stub is created. Further, the derived stub generation unit 13 adds the stub class name of the generated derived stub to the corresponding record in the cast set 22.

Further, the derived stub generation unit 13 modifies the description of return in the body part of the called method in the derived stub so that the object corresponding to the cast destination class is instantiated and returned.

The update unit 14 detects a statement corresponding to the information of each record stored in the cast set 22 in the test target class. The update unit 14 updates the stub class name of the stub to be called in the detected statement to the stub class name of the derived stub included in the corresponding record.

The stub generator 10 can be realized by, for example, the computer 60 shown in FIG. The computer 60 includes a Central Processing Unit (CPU) 61, a memory 62 as a temporary storage area, and a non-volatile storage unit 63. Further, the computer 60 is connected to an input / output device 64 such as a display device and an input device, a read / write (R / W) unit 65 that controls reading and writing of data to a storage medium 69, and a network such as the Internet. The network interface (I / F) 66 is provided. The CPU 61, the memory 62, the storage unit 63, the input / output device 64, the R / W unit 65, and the network I / F 66 are connected to each other via the bus 67.

The storage unit 63 can be realized by a Hard Disk Drive (HDD), a solid state drive (SSD), a flash memory, or the like. The storage unit 63 as a storage medium stores a stub generation program 70 for causing the computer 60 to function as the stub generation device 10.

The CPU 61 reads the stub generation program 70 from the storage unit 63, expands the stub generation program 70 into the memory 62, and sequentially executes the processes included in the stub generation program 70. The stub generation program 70 includes a stub generation process 71, an analysis process 72, a derived stub generation process 73, and an update process 74. The CPU 61 operates as the stub generation unit 11 shown in FIG. 1 by executing the stub generation process 71. Further, the CPU 61 operates as the analysis unit 12 shown in FIG. 1 by executing the analysis process 72. Further, the CPU 61 operates as the derived stub generation unit 13 shown in FIG. 1 by executing the derived stub generation process 73. Further, the CPU 61 operates as the update unit 14 shown in FIG. 1 by executing the update process 74. As a result, the computer 60 that has executed the stub generation program 70 functions as the stub generation device 10.

The function realized by the stub generation program 70 can also be realized by, for example, a semiconductor integrated circuit, more specifically, an Application Specific Integrated Circuit (ASIC) or the like.

Next, the operation of the stub generator 10 according to the present embodiment will be described. When the test target class is input to the stub generation device 10, the stub generation device 10 executes the stub generation process shown in FIG. Here, it is assumed that the test target class in which the inheritance relationship between the classes as shown in FIG. 9 is defined is input. FIG. 9 shows an example in which the child classes “orange” and “banana” inheriting the parent class “fruit” and the child classes “cat” and “dog” inheriting the parent class “animal” are defined. There is. Further, as shown in FIG. 10, class 41A (class name "stub A") and class 41B (class name "stub B") are defined as user-defined classes called from the method of the test target class 31. In the following, a case where the original classes 41A and 41B are set as stub target classes will be described.

In step S11 of the stub generation process shown in FIG. 8, the stub generation unit 11 stubs the original classes 41A and 41B to be stubized, and stubs 42A (stub class name “stub A”) and stub 42B (stub class name). "Stub B") is generated. Here, as shown in FIG. 11, stubs 42A and 42B that return an instance of the return type object of the method that calls the original class are generated.

Next, in step S12, the analysis unit 12 stores the stub class name of the stub generated by the stub generation unit 11 in the stub set 21. Here, the stub class names "stub A" and "stub B" are stored in the stub set 21.

Next, in step S13, the analysis unit 12 calls the stub indicated by the stub class name stored in the stub set 21 from the test target class 31, and extracts all statements in which the object returned from the stub is cast. To do. The analysis unit 12 can extract, for example, a statement including a description indicating the cast (in the present embodiment, a description in which the cast destination class is described in (), such as “(mandarin orange)”).

Next, in step S14, the analysis unit 12 acquires information on the class to which the object is cast, the stub class name of the stub to be called, and the method name of the method that calls the stub from each of the extracted statements. For example, as shown in FIG. 12, in the present embodiment, the analysis unit 12 acquires the cast destination class from the inside of () in the statement, and the part before the “. (Dot)” in the subsequent description is the stub class. You can get the name and the latter part as the method name.

The analysis unit 12 creates a record from the acquired information and stores it in the cast set 22. FIG. 13 shows an example of records stored in the cast set 22 from each statement of the test target class 31. The statement on the third line of the test target class 31 (broken line portion in FIG. 13) is not extracted in step S13 because it does not include a description indicating the cast.

Next, in step S15, the derived stub generation unit 13 sets the variable i for specifying the record stored in the cast set 22 to the initial value 0.

Next, in step S16, the derived stub generation unit 13 determines whether or not the variable i is smaller than the number of records stored in the cast set 22. If i <the number of records in the cast set, the process proceeds to step S17.

In step S17, the derived stub generation unit 13 sets the i-1st record stored in the cast set 22 to the records to be processed in the following steps S18 to S21.

Next, in step S18, the derived stub generation unit 13 duplicates the stub code indicated by the stub class name included in the record to be processed to generate the derived stub. When the record 51 to be processed (the record in the first row of the cast set 22 shown in FIG. 13) is set as shown in FIG. 14, the stub 42A (stub class name “stub”” from the “stub class name” of the record 51 is set. A ") is specified. Then, this stub 42A is duplicated to generate a derivative stub 43A.

Next, in step S19, the derived stub generation unit 13 adds “derivative i” after the class name (“stub A”) of the original stub class, as shown by the broken line portion P in FIG.

Next, in step S20, the description of return in the body part of the called method in the derived stub is modified so that the derived stub generation unit 13 instantiates and returns the object corresponding to the cast destination class. The broken line part Q in FIG. 14 is an example in which the object of the child class “Mikan”, which is the cast destination class, is instantiated and the object upcast to the parent class “Fruit” is returned. In this case, the return destination will be the downcast after the upcast, and the class cast will be performed appropriately.

Next, in step S21, the derived stub generation unit 13 adds the generated stub class name of the derived stub to the record to be processed in the cast set 22 as shown by the arrow R in FIG.

Next, in step S22, the derivative stub generation unit 13 increments the variable i by 1, and the process returns to step S16. In the present embodiment, by the iterative processing of steps S16 to S22, the stub A derivative 1 is derived from the record in the second row of the cast set 22 shown in FIG. The stub B derivative 3 is generated. If it is determined in step S16 that i exceeds the number of records in the cast set 22, the process proceeds to step S23.

In step S23, the update unit 14 detects a statement corresponding to the information of each record stored in the cast set 22 in the test target class 31. Then, as shown in FIG. 15, the update unit 14 updates the stub class name of the stub to be called in the detected statement to the stub class name of the derived stub included in the corresponding record. In the statements on lines 4 to 7 of FIG. 15, the stub to be called is updated to the derived stub generated by the derived stub generator 13. Also, in the statement on the third line, the returned object is not cast, so the stub to be called remains the original stub generated by the stub generator 11.

When the update of the stub class name by the update unit 14 is completed, the stub generated by the stub generation unit 11 and the derived stub generated by the derivative stub generation unit 13 are output, and the stub generation process ends.

FIG. 16 schematically shows a stub call from the test target class 31. Derived stub 43A0 (stub class name "stub A derived 0") is called from the statement on the fourth line of the test target class 31. Further, the derived stub 43A1 (stub class name "stub A derivative 1") is called from the statement on the fifth line. In addition, the derived stub 43A2 (stub class name "stub A derivative 2") is called from the statement on the sixth line. Further, the derived stub 43B (stub class name "stub B derivative 3") is called from the statement on the fifth line. The original stub 42A (stub class name "stub A") is called from the statement on the third line.

As described above, the stub generator according to the present embodiment generates a stub that is a dummy of the class called from the method of the test target class. If this stub is used as it is, as shown in FIG. 17, the object returned from the stub may be downcast at the return destination, and an exception may occur. Therefore, in the present embodiment, as shown in FIG. 18, a derived stub that returns an object according to the cast destination class is generated from the original stub. Then, in the test target class, the stub to be called is updated to the derived stub. As a result, the occurrence of downcast can be suppressed. If the class is called from a statement without a cast, the original stub is called.

As a result, it is possible to prevent the symbolic execution of the test target class from being interrupted due to a class cast error, and thus it is possible to suppress a decrease in test completeness.

As described above, the error occurs in the case of downcast. Therefore, in the above embodiment, the case where only the downcast is handled as the classcast has been described, but the disclosed technique can be applied to the test target class in which the upcast is mixed. In this case, the derived stub may be generated when the returned object is cast without distinguishing between the downcast and the upcast. In the case of upcast, the class of the object returned from the derived stub is the same as the class of the object returned from the original stub, so there is no problem. It should be noted that the derived stub may be generated only in the case of downcast by referring to the inheritance relationship of the class as shown in FIG. In this case, it is possible to suppress the generation of unnecessary derivative stubs.

Further, in the above embodiment, the case where the class and method described in Java (registered trademark) is used as the program to be tested has been described, but the present invention is not limited to this. The disclosed technique is applicable to programs written in other languages, especially programs written in object-oriented languages.

Further, in the above description, the mode in which the stub generation program 70 is stored (installed) in the storage unit 63 in advance has been described, but the present invention is not limited to this. The program according to the disclosed technology can also be provided in a form recorded on a storage medium such as a CD-ROM, a DVD-ROM, or a USB memory.

Regarding the above embodiments, the following additional notes will be further disclosed.

(Appendix 1)
A first generator that creates a first stub that returns a dummy object in response to a class call from the program under test,
When the object returned from the first stub generated by the first generation unit is type-converted at the return destination, the object corresponding to the type conversion at the return destination of the object based on the first stub. A second generator that generates a second stub that returns
In the test target program, an update unit that updates the target of a class call involving type conversion from the first stub to a second stub generated based on the first stub.
Stub generator including.

(Appendix 2)
The first generation unit generates a first stub that returns an object according to the type of the class.
In the first stub, the second generation unit includes a description indicating that an object corresponding to the type of the class is returned, and a description indicating that an object of a type that does not cause an error during type conversion of the return destination is returned. The stub generator according to Appendix 1, which generates a second stub by rewriting to.

(Appendix 3)
The second generation unit extracts a description indicating a class call accompanied by type conversion from the test target program, and the first generation unit is generated for the class call included in the extracted description. The stub generation device according to Appendix 2, which generates the second stub by duplicating one stub and rewriting the description regarding the return of an object in the duplicated first stub.

(Appendix 4)
Generates a first stub that returns a dummy object in response to a class call from the program under test.
When the object returned from the generated first stub is type-converted at the return destination, the second stub that returns the object corresponding to the type conversion at the return destination of the object based on the first stub. To generate
In the test target program, a stub generation in which a computer executes a process including updating the target of a class call involving type conversion from the first stub to a second stub generated based on the first stub. Method.

(Appendix 5)
As the first stub, a first stub that returns an object according to the type of the class is generated.
The second stub is described in the first stub to indicate that an object corresponding to the type of the class is returned, and a description indicating that an object of a type that does not cause an error during type conversion of the return destination is returned. The stub generation method according to Appendix 4, which is generated by rewriting.

(Appendix 6)
From the program under test, a description indicating a class call with type conversion is extracted, the first stub generated for the class call included in the extracted description is duplicated, and the object in the duplicated first stub is duplicated. The stub generation method according to Appendix 5, wherein the second stub is generated by rewriting the description regarding the return of the stub.

(Appendix 7)
Generates a first stub that returns a dummy object in response to a class call from the program under test.
When the object returned from the generated first stub is type-converted at the return destination, the second stub that returns the object corresponding to the type conversion at the return destination of the object based on the first stub. To generate
In the test target program, for causing a computer to execute a process including updating the target of a class call involving type conversion from the first stub to a second stub generated based on the first stub. Stub generator.

(Appendix 8)
As the first stub, a first stub that returns an object according to the type of the class is generated.
The second stub is described in the first stub to indicate that an object corresponding to the type of the class is returned, and a description indicating that an object of a type that does not cause an error during type conversion of the return destination is returned. The stub generation program according to Appendix 7, which is generated by rewriting.

(Appendix 9)
From the program under test, a description indicating a class call with type conversion is extracted, the first stub generated for the class call included in the extracted description is duplicated, and the object in the duplicated first stub is duplicated. The stub generation program according to Appendix 8, which generates the second stub by rewriting the description regarding the return of the stub.

(Appendix 10)
Generates a first stub that returns a dummy object in response to a class call from the program under test.
When the object returned from the generated first stub is type-converted at the return destination, the second stub that returns the object corresponding to the type conversion at the return destination of the object based on the first stub. To generate
In the test target program, for causing a computer to execute a process including updating the target of a class call involving type conversion from the first stub to a second stub generated based on the first stub. A storage medium that stores a stub generator.

10 Stub generator 11 Stub generator 12 Analysis unit 13 Derived stub generator 14 Update unit 21 Stub set 22 Cast set 31 Test target class 41 Original class 42 Stub 43 Derived stub 60 Computer 61 CPU
62 Memory 63 Storage unit 69 Storage medium 70 Stub generation program

Claims (5)

The class that is called from the method included in the test target program to stubbing, a first generator for generating a first stub to return a dummy object,
When the object returned from the first stub generated by the first generation unit is type-converted at the return destination, an object capable of type conversion at the return destination of the object based on the first stub. A second generator that generates a second stub that returns
In the test target program, an update unit that updates the target of the class in which the returned object is type-converted at the return destination from the first stub to the second stub generated based on the first stub.
Stub generator including. The first generation unit generates a first stub that returns an object according to the type of the class.
In the first stub, the second generation unit includes a description indicating that an object corresponding to the type of the class is returned, and a description indicating that an object of a type that does not cause an error during type conversion of the return destination is returned. The stub generator according to claim 1, wherein the second stub is generated by rewriting the stub. The second generation unit extracts a description indicating a class call accompanied by type conversion from the test target program, and the first generation unit is generated for the class call included in the extracted description. The stub generator according to claim 2, wherein the second stub is generated by duplicating one stub and rewriting the description regarding the return of the object in the duplicated first stub. Stub the class called from the method included in the program under test, generate the first stub that returns a dummy object,
When the object returned from the generated first stub is type-converted at the return destination, the second stub that returns an object that can be type-converted at the return destination of the object based on the first stub. To generate
In the test target program, a process including updating the call target of the class whose return object is type-converted at the return destination from the first stub to the second stub generated based on the first stub. How to generate stubs that your computer does. Stub the class called from the method included in the program under test, generate the first stub that returns a dummy object,
When the object returned from the generated first stub is type-converted at the return destination, the second stub that returns an object that can be type-converted at the return destination of the object based on the first stub. To generate
In the test target program, a process including updating the call target of the class in which the returned object is type-converted at the return destination from the first stub to the second stub generated based on the first stub. A stub generator that lets your computer run.

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