JP2018147388A - Stub generator, method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stub generator that generates a stub for suppressing a reduction of test coverage in symbolic execution of a program under test that includes conversion of object types.SOLUTION: In a stub generator 10, a stub generation unit 11 generates a stub that returns a dummy object in response to class invocation from a class under test. When an object returned from an original stub has its type converted at the return destination, a derived stub generation unit 13 generates a derived stub, on the basis of the stub, that returns an object that corresponds to the type conversion at the return destination of the object. An updating unit 14 updates, in the program under test, the subject of invocation of a class that involves type conversion from an original stub to a derived stub generated on the basis of the original stub.SELECTED DRAWING: Figure 1

Description

  The disclosed technology relates to a stub generation device, a stub generation method, and a stub generation program.

  In the program test technology by symbolic execution, when generating a test case, a driver that constructs and sets a test environment and a stub that is a dummy implementation of a program component that is called by a test target program are prepared. Yes.

  For example, a system including module execution means for executing a module to be tested, a dependent module called from the module, and a stub acting as a procedure of the procedure performed by the dependent module in accordance with the contents of each description. Proposed. The module execution means detects a call from the test target module to the dependent module, determines whether the module is a dependent module or a stub as a module for executing the calling process, and executes the calling process according to the determination. Including a processing delegation means.

  Also proposed is an information processing device that inputs a target program and path information on the target program, and generates a stub program that represents changes in accordance with path information of variable values updated by an external program called from the target program Has been. This apparatus 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 an initial value of path information.

JP 2009-129133 A JP 2012-181666 A

  When assigning an object to a variable in a target program in which an inheritance relationship between classes included in the target program is defined, it is necessary to type-convert the object into an appropriate class.

  However, depending on the inheritance relationship between the object type 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 time, and the test coverage is deteriorated.

  An object of the disclosed technique is to generate a stub that suppresses a decrease in test completeness in symbolic execution of a test target program including object type conversion.

  As an aspect of the disclosed technology, the first generation unit generates a first stub that returns a dummy object in response to a class call from a test target program. When the object returned from the first stub generated by the first generator is type-converted at the return destination, the second generator is based on the first stub at the return destination of the object. A second stub that returns an object corresponding to type conversion is generated. The updating unit updates the class call target accompanied with type conversion in the test target program from the first stub to the second stub generated based on the first stub.

  As one aspect, there is an effect that it is possible to generate a stub that suppresses a decrease in test completeness in symbolic execution of a test target program including object type conversion.

It is a functional block diagram of the stub production | generation apparatus which concerns on this embodiment. It is a figure for demonstrating the procedure of the unit test of the program using a symbolic execution technique. It is a figure which shows an example of the default value for every return type of the method of a primitive type. It is a figure for demonstrating stub generation in case a return type is a primitive. It is a figure for demonstrating stub generation in case a return type is an object of a user designation type. It is a figure for demonstrating exception generation by a downcast. It is a block diagram which shows the outline of the computer which functions as a stub production | generation apparatus concerning this embodiment. It is a flowchart which shows an example of the stub production | generation process in this embodiment. It is a figure which shows the inheritance relationship between the classes in a test object class. It is a figure which shows an example of a test object class. It is a figure for demonstrating the production | generation of an original stub. It is a figure for demonstrating the statement containing a class cast. It is a figure which shows an example of a cast set. It is a figure for demonstrating the production | generation of a derived stub. It is a figure which shows an example of the update of the stub class name in a test object class. It is a figure which shows the call of the stub from a test object class. It is a figure for demonstrating the case where an original stub is called. It is a figure for demonstrating the case where a derivative stub is called.

  Hereinafter, an exemplary embodiment related to the disclosed technology will be described in detail with reference to the drawings. In the present embodiment, a case where the test target program is a class and a method described in Java (registered trademark) will be described as an example.

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

  Here, the procedure of the unit test of the program using the symbolic execution technique 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 constructs and sets the execution environment of the test target class 31 and starts the test target class. A stub is a dummy implementation of a program component called by a test target class. The program component called from the test target class may be in the process of being mounted or the program component may not be tested at the test stage of the test target class. In addition, the program component may execute external access to a file, a database, or the like. For this reason, when a program part called from a test target class cannot be used during a test, a stub is used instead of the actual program part.

  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 using the generated test case, the unit test tool 201 executes a test, thereby obtaining a test result for the test target class (S103).

  For stub generation, this is a class that is called from a method included in the test target class, and the return value type (hereinafter referred to as “return type”) to each method from the stub target class is a primitive type. Think. In this case, as shown in FIG. 3, for example, a stub that returns a default value determined in advance according to the method return type is generated without the mounting body. 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. If the example of FIG. 3 is used, since the default value for the return type “int” is “0”, a code (“return 0”) that returns 0 is described in the body portion of method1. In addition, when the return type is “void” as in method 2 included in the original class (StubSample), nothing is returned from the stub, so the body part remains empty. In this way, the original class is stubbed. That is, a stub is generated.

  Further, regarding the generation of stubs, consider a case where the return type of a method that calls a class to be stubbed is a user-specified type. For example, it is assumed that the return type “Class A” of method 1 that calls a 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 a location where the return value “Null” is accessed in the test target class. In order to avoid this exception occurrence, a stub that returns an instance of a user-specified type object is generated. Default values are passed for each argument of the constructor.

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

  For example, the class cast in the case where the child class “Child” inherits the parent class “Parent” has the following pattern.

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

  In the above (1), “new Child ()” represents instantiating an object of the child class “Child”, and “(Parent)” represents casting the object to the parent class “Parent”. “Parent p =” represents that an object is assigned to the variable p of the parent class “Parent”. That is, the above (1) represents up-casting, and such class casting is possible.

  In the above (2), the instantiated object of the child class “Child” 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 down-casting the instantiated object of the parent class “Parent” to the child class “Child”, and such class casting is not possible.

  Next, problems that occur when an object returned from a stub is class-casted in a test target class will be described.

  As shown in FIG. 6, from the original class called from the test target class, the object p up-casted from the child class “Child” to the parent class “Parent” is returned. 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 upcasting, class casting is possible.

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

  Therefore, in this embodiment, a stub that returns an object corresponding to the class cast at the return destination of the object is generated. Hereinafter, each part of the stub generation device 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 derived stub generation unit 13, and an update unit 14. The stub generation unit 11 is an example of a first generation unit according to the disclosed technique, and the analysis unit 12 and the derived stub generation unit 13 are examples of a second generation unit according to the disclosed technique.

  The stub generation unit 11 stubs a stub object class called from a method included in the input test object class, and generates a stub called at the time of symbolic execution. Since a stub generation method by the stub generation unit 11 can use a conventionally known method, detailed description thereof is omitted in the present embodiment.

  The analysis unit 12 specifies 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 class names (hereinafter referred to as “stub class names”) of stubs (stubbed classes) generated by the stub generation unit 11 and stores them in the stub set 21. In addition, the analysis unit 12 calls out 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 objects returned from the stub are cast. The analysis unit 12 obtains information on the object cast destination class, the stub class name of the called stub, and the method name of the method calling the stub from each extracted statement. The analysis unit 12 creates a record from the acquired information and stores it in the cast set 22.

  The derivation stub generation unit 13 generates a stub that returns an object corresponding to a cast destination class from 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 “derived stub”.

  Specifically, the derived stub generation unit 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 in which “derivative i” is added after the stub class name of the original stub. i can be an integer counting up from 0 each time a derived stub is generated. In addition, 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.

  Also, the derived stub generation unit 13 modifies the description of return in the body part of the callee method in the derived stub so as to instantiate and return an object corresponding to the cast destination class.

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

  The stub generation device 10 can be realized, for example, by a 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 nonvolatile storage unit 63. 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 with respect to the storage medium 69, and a network such as the Internet. A 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 a 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 and expands it in 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 illustrated in FIG. 1 by executing the stub generation process 71. Further, the CPU 61 operates as the analysis unit 12 illustrated in FIG. 1 by executing the analysis process 72. Further, the CPU 61 operates as the derived stub generation unit 13 illustrated in FIG. 1 by executing the derived stub generation process 73. The CPU 61 operates as the update unit 14 illustrated 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 be realized by, for example, a semiconductor integrated circuit, more specifically, an application specific integrated circuit (ASIC).

  Next, the operation of the stub generation device 10 according to this embodiment will be described. When the test target class is input to the stub generation device 10, the stub generation processing shown in FIG. 8 is executed in the stub generation device 10. Here, it is assumed that a test target class in which an inheritance relationship between classes as shown in FIG. 9 is defined is input. FIG. 9 shows an example in which child classes “mandarin orange” and “banana” that inherit the parent class “fruit” and child classes “cat” and “dog” that inherit the parent class “animal” are defined. Yes. Also, as shown in FIG. 10, a class 41A (class name “stub A”) and a 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 these 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 converts the original classes 41A and 41B to be stubbed into stubs, and stub 42A (stub class name “stub A”) and stub 42B (stub class name). “Stub B”). Here, as shown in FIG. 11, stubs 42A and 42B that return instances of return type objects of methods that call the original class are generated.

  Next, in step S <b> 12, 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 objects returned from the stub are cast. To do. The analysis unit 12 can extract, for example, a statement including a description indicating a cast (in this embodiment, a description indicating a cast destination class in () like “(Mikan)”).

  Next, in step S14, the analysis unit 12 acquires information on the object cast destination class, the stub class name of the stub to be called, and the method name of the method that calls the stub from each extracted statement. For example, as shown in FIG. 12, in this embodiment, the analysis unit 12 acquires a cast destination class from within () in a statement, and sets the preceding part of “. (Dot)” in the subsequent description as a stub class. Name and back part can be obtained as 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. Note that the statement on the third line of the test target class 31 (broken line portion in FIG. 13) does not include the description indicating the cast, and thus is not extracted in step S13.

  Next, in step S <b> 15, the derived stub generation unit 13 sets a variable i for specifying a record stored in the cast set 22 to an initial value of 0.

  Next, in step S <b> 16, the derived stub generation unit 13 determines whether the variable i is smaller than the number of records stored in the cast set 22. If i <number of records in the cast set, the process proceeds to step S17.

  In step S <b> 17, the derived stub generation unit 13 sets the i−1th record stored in the cast set 22 as a record to be processed in the following steps S <b> 18 to S <b> 21.

  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 a derived stub. As shown in FIG. 14, when the record 51 to be processed (record on the first line of the cast set 22 shown in FIG. 13) is set, the stub 42A (stub class name “stub” from the “stub class name” of the record 51 is set. A ") is identified. The stub 42A is duplicated to generate a derived stub 43A.

  Next, in step S19, the derivation stub generation unit 13 adds “derivation i” after the class name (“stub A”) of the original stub class, as indicated by a broken line part P in FIG.

  Next, in step S20, the derived stub generation unit 13 modifies the description of return in the body part of the callee method in the derived stub so that the object corresponding to the cast destination class is instantiated and returned. A broken line portion Q in FIG. 14 is an example in which an object of a child class “mandarin orange” which is a cast destination class is instantiated and an object upcast to the parent class “fruit” is returned. In this case, the return destination is a downcast after the upcast, and the class cast is appropriately performed.

  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 indicated by an arrow R in FIG.

  Next, in step S22, the derived stub generation unit 13 increments the variable i by 1, and the process returns to step S16. In the present embodiment, from the records in the second row of the cast set 22 shown in FIG. 13, the stub A derivation 1 from the third row record to the stub A derivation 2 and the records in the fourth row are performed by repeating the steps S16 to S22. Stub B derivation 3 is generated. If it is determined in step S16 that i has exceeded the number of records in the cast set 22, the process proceeds to step S23.

  In step S <b> 23, 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 illustrated 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 the 4th to 7th lines in FIG. 15, the stub to be called is updated to the derived stub generated by the derived stub generation unit 13. In the statement on the third line, since the return object is not cast, the stub to be called is the original stub generated by the stub generation unit 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 derived 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. The 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. Also, the derivation stub 43A1 (stub class name “stub A derivation 1”) is called from the statement on the fifth line. Further, the stub 43A2 (stub class name “stub A derivation 2”) is called from the statement on the sixth line. Also, the derivation stub 43B (stub class name “stub B derivation 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 generation device according to the present embodiment generates a stub that is a dummy of a class called from a method of a test target class. When this stub is used as it is, as shown in FIG. 17, an object returned from the stub is 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 corresponding to the cast destination class is generated from the original stub. Then, the stub to be called is updated to the derived stub in the test target class. Thereby, generation | occurrence | production of a downcast can be suppressed. When calling a class 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 coverage.

  As described above, the error occurs in the case of downcast. Therefore, in the above-described embodiment, the case where only the downcast is handled as the class cast has been described. However, the disclosed technique can be applied to the test target class in which the upcast is mixed. In this case, a derived stub may be generated when a return object is cast without distinguishing between downcasting and upcasting. In the case of upcasting, 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. Note that the derived stub may be generated only in the case of downcast with reference to the class inheritance relationship as shown in FIG. In this case, generation of unnecessary derived stubs can be suppressed.

  In the above-described embodiment, a case has been described in which a class and a method described in Java (registered trademark) are programs to be tested. However, the present invention is not limited to this. The disclosed technique can be applied to a program written in another language, particularly a program written in an object-oriented language.

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

  Regarding the above embodiment, the following additional notes are disclosed.

(Appendix 1)
A first generation unit that generates a first stub that returns a dummy object in response to a class call from a test target program;
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 for generating a second stub for returning
In the test target program, an update unit that updates a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub;
A stub generator.

(Appendix 2)
The first generation unit generates a first stub that returns an object corresponding 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 at the time of type conversion of the return destination is returned. The stub generation device according to attachment 1, wherein the second stub is generated by rewriting to

(Appendix 3)
The second generation unit extracts a description indicating class call accompanied by type conversion from the test target program, and the first generation unit generated by the first generation unit with respect to the class call included in the extracted description The stub generation device according to attachment 2, wherein the stub is generated by duplicating one stub and rewriting a description related to returning the object in the copied first stub.

(Appendix 4)
Generate a first stub that returns a dummy object in response to a class call from the test target program,
The second stub that returns an object corresponding to the type conversion at the return destination of the object based on the first stub when the object returned from the generated first stub is type-converted at the return destination. Produces
In the test target program, a stub generation in which a computer executes processing including updating a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub Method.

(Appendix 5)
As the first stub, generate a first stub that returns an object corresponding to the type of the class,
In the first stub, the second stub is replaced with 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 at the time of type conversion of the return destination is returned. The stub generation method according to attachment 4, wherein the stub generation method is generated by rewriting.

(Appendix 6)
A description indicating class call accompanied by type conversion is extracted from the test target program, the first stub generated for the class call included in the extracted description is copied, and the object in the copied first stub is copied The stub generation method according to appendix 5, wherein the second stub is generated by rewriting a description related to the return of the stub.

(Appendix 7)
Generate a first stub that returns a dummy object in response to a class call from the test target program,
The second stub that returns an object corresponding to the type conversion at the return destination of the object based on the first stub when the object returned from the generated first stub is type-converted at the return destination. Produces
In the test target program, for causing a computer to execute a process including updating a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub. Stub generator.

(Appendix 8)
As the first stub, generate a first stub that returns an object corresponding to the type of the class,
In the first stub, the second stub is replaced with 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 at the time of type conversion of the return destination is returned. The stub generation program according to appendix 7, which is generated by rewriting.

(Appendix 9)
A description indicating class call accompanied by type conversion is extracted from the test target program, the first stub generated for the class call included in the extracted description is copied, and the object in the copied first stub is copied The stub generation program according to supplementary note 8, wherein the second stub is generated by rewriting a description related to return of the stub.

(Appendix 10)
Generate a first stub that returns a dummy object in response to a class call from the test target program,
The second stub that returns an object corresponding to the type conversion at the return destination of the object based on the first stub when the object returned from the generated first stub is type-converted at the return destination. Produces
In the test target program, for causing a computer to execute a process including updating a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub. A storage medium storing a stub generation program.

DESCRIPTION OF SYMBOLS 10 Stub production | generation apparatus 11 Stub production | generation part 12 Analysis part 13 Derived stub production | generation part 14 Update part 21 Stub set 22 Cast set 31 Test object 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)

A first generation unit that generates a first stub that returns a dummy object in response to a class call from a test target program;
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 for generating a second stub for returning
In the test target program, an update unit that updates a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub;
A stub generator. The first generation unit generates a first stub that returns an object corresponding 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 at the time of type conversion of the return destination is returned. The stub generation device according to claim 1, wherein the second stub is generated by rewriting to:   The second generation unit extracts a description indicating class call accompanied by type conversion from the test target program, and the first generation unit generated by the first generation unit with respect to the class call included in the extracted description The stub generation device according to claim 2, wherein the second stub is generated by duplicating one stub and rewriting a description related to returning an object in the copied first stub. Generate a first stub that returns a dummy object in response to a class call from the test target program,
The second stub that returns an object corresponding to the type conversion at the return destination of the object based on the first stub when the object returned from the generated first stub is type-converted at the return destination. Produces
In the test target program, a stub generation in which a computer executes processing including updating a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub Method. Generate a first stub that returns a dummy object in response to a class call from the test target program,
The second stub that returns an object corresponding to the type conversion at the return destination of the object based on the first stub when the object returned from the generated first stub is type-converted at the return destination. Produces
In the test target program, for causing a computer to execute a process including updating a target of a class call accompanied by type conversion from the first stub to a second stub generated based on the first stub. Stub generator.