Abstract:
In a method for testing a program, repeated measurement on branches that are frequently taken is prevented, thereby avoiding unnecessary overhead. An information processing device includes a coverage measurement control program for determining whether the number of times an instruction of a measurement target program has been executed due to execution of the measurement target program is equal to or larger than the maximum allowable number of measurements set for the instruction; and a coverage measurement program for incrementing a value in a field for the instruction by one to indicate the number of times the instruction has been executed, the coverage measurement program being called if the number of times the instruction has been executed is smaller than the maximum allowable number of measurements.

Description:
CLAIM OF PRIORITY  
       [0001]     The present application claims priority from Japanese application P2004-157216 filed on May 27, 2004, the content of which is hereby incorporated by reference into this application.  
       FIELD OF THE INVENTION  
       [0002]     The present invention relates to a technique of testing a program that is executed by an information processing apparatus.  
       BACKGROUND OF THE INVENTION  
       [0003]     Coverage measurement tools have been used to improve the quality of software and thereby prevent software failure. Conventional techniques for coverage measurement tools are described in, e.g., Japanese Patent Laid-open Nos. 5-334126 (Patent Document 1), 5-324402 (Patent Document 2), and 10-320190 (Patent Document 3).  
         [0004]     A description will be given below of conventional coverage measurement techniques disclosed in these patent publications. It should be noted that even through some documents use the term “coverage analyzer” to refer to a tool for performing coverage measurement, this specification uses the term “coverage measurement tool” instead.  
         [0005]     Coverage measurement tools have been used to check the quality of complete software. Coverage measurement tools have the so-called C0 coverage function and C1 coverage function. The C0 coverage function checks whether memory has been accessed by the program under test, while the C1 coverage function checks which branch of a conditional branch instruction of the program under test has been taken.  
         [0006]     The C0 coverage is calculated based on the total number of instructions (or lines) to be executed in the program and the number of instructions (or lines) actually executed when the program was executed. The C1 coverage, on the other hand, is calculated based on the total number of branches to be taken in the program and the number of branches actually taken when the program was executed.  
         [0007]     That is: 
 
 C 0 coverage (%)=(number of instructions actually executed)/(total number of instructions to be executed)×100, and 
 
 C 1 coverage (%)=(number of branches actually taken)/(total number of branches to be taken)×100. 
 
         [0008]     Referring to  FIG. 3 , in C0 coverage measurement, if execution of a conditional branch instruction in the program under test causes the FALSE branch of the instruction to be taken, the coverage test fails to check the TRUE branch. This means that the test may be able to check only either the TRUE branch or FALSE branch. In the case of C1 coverage measurement, on the other hand, both branches can be comprehensively checked.  
         [0009]     A description will be given below of an exemplary method for achieving coverage measurement, specifically C1 coverage measurement. When the program to be tested includes a conditional branch instruction (such as the instruction code  4  shown in  FIG. 3 ), the compiler, assembler, etc. for the source program inserts a jump instruction (or possibly a software interrupt instruction) at a point immediately before the conditional branch instruction in order to jump to coverage measurement program code for performing C1 coverage measurement on the conditional branch instruction. (The instruction code  3  shown in  FIG. 4  is the inserted jump instruction code.) When the program shown in  FIG. 4  is executed, execution of the instruction code  3  causes processing to jump to the coverage measurement program code. The coverage measurement program checks the execution address of the instruction code  3  and the state of a CPU flag to determine whether the TRUE branch or FALSE branch of the instruction code  4  immediately succeeding the instruction code  3  will be taken when the instruction code  4  is executed. Then, processing returns to the program under test after storing the determination result.  
         [0010]     The determination result, that is, data as to which branch of the instruction code  4  has been taken, is stored in a table as shown in  FIG. 5 . Specifically, if it is the TRUE branch, the coverage measurement program increments the value in the field  1710  in the table by one to indicate the number of times the TRUE branch of the instruction code  4  has been taken. If, on the other hand, the CPU flag indicates the FALSE branch, the coverage measurement program increments the value in the field  1711  in the table by one to indicate the number of times the FALSE branch has been taken. It should be noted that such a table is often generated by a compiler, assembler, etc. when it inserts the instruction code  3 .  
         [0011]     Upon completion of the execution, the tested program is processed based on the above stored data and the results are output. When each instruction code of the measurement target program was generated using high-level language code through a language processor such as a compiler, some coverage measurement tools also output information for associating each processing statement in the high-level language code with the above stored data as to which branch was taken and how many times in order to increase the test efficiency. After completion of the test, the inserted jump instruction (the instruction code  3 ) for coverage measurement is deleted to restore the original program code shown in  FIG. 3 . Then, the program is shipped as a software product.  
         [0012]     The above method for coverage measurement has the problem of involving CPU overhead since it inserts a jump instruction at a point immediately before each target conditional branch instruction and executes it to determine the coverage. This overhead significantly reduces the execution speed, making it difficult to test a program which requires real-time processing. As a result, the test produces only reduced effect. This problem also arises with C0 coverage measurement.  
         [0013]     Further, a conventional coverage measurement tool performs coverage measurement on the same branch repeatedly (that is, stores the number of times the branch has been taken) even when the branch is frequently taken. Repeated measurement on such a branch, that is, storing the number of times such a branch has been taken, is often unnecessary. The reason for this is that the calculation of C0 coverage or C1 coverage of a branch only requires information on whether the branch has ever been taken at least once (it does not matter how many times it has been taken). It is often unnecessary to check the same measurement point more than once. That is, preventing repeated measurement on branches that are frequently taken may lead to a reduction in the measurement time and an increase in the efficiency of the debugging process.  
         [0014]     It should be noted that even though Patent Documents 1 to 3 each propose some technique for reducing the time required for coverage measurement, they do not satisfy the requirement of preventing repeated measurement on branches which are frequently taken.  
         [0015]     It is, therefore, an object of the present invention to provide a method for testing a program, capable of preventing repeated measurement on branches that are frequently taken and thereby avoiding unnecessary overhead.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention provides a technique for testing a program, which initially counts the number of times each instruction, or at least each branch instruction, of the program has been executed, but stops counting when the count has reached a predetermined value.  
         [0017]     The present invention can avoid counting the number of times each branch has been taken when the count has reached a desired value and thereby eliminate unnecessary overhead. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is a diagram showing the configuration of an information processing device according to an embodiment of the present invention;  
         [0019]      FIG. 2  is a diagram showing an exemplary structure of a measurement target program;  
         [0020]      FIG. 3  is a diagram showing an exemplary original structure of the measurement target program;  
         [0021]      FIG. 4  is a diagram showing an exemplary conventional structure of the measurement target program;  
         [0022]      FIG. 5  is a diagram showing the configuration of a measurement record table according to the embodiment;  
         [0023]      FIG. 6  is a diagram showing the configuration of a measurement condition setting table according to the embodiment; and  
         [0024]      FIG. 7  is a diagram showing the processing procedure performed by a coverage measurement control program according to the embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]     A preferred embodiment of the present invention will be described with reference to the accompanying drawings.  
       First Embodiment  
       [0026]      FIG. 1  shows a system configuration according to a first embodiment of the present invention. Referring to the figure, an information processing device  1  includes a program execution device  11  for executing a measurement target program  12 . The measurement target program  12  is subjected to coverage measurement.  
         [0027]     The program execution device  11  includes a CPU and memory and executes the OS, an interpreter program, and other programs stored in the memory.  
         [0028]     Still referring to  FIG. 1 , the information processing device  1  also includes an external storage device  13  and working memory  14 . The external storage device  13  stores various programs and data and may be a disk drive, a memory card, magnetic tape, or the like. According to the present embodiment, the external storage device  13  stores the measurement target program  12 , a coverage measurement program  15 , a coverage measurement control program  16 , a measurement point setting program  20 , a measurement record table  17 , and a measurement condition setting table  18 , as described later.  
         [0029]     The working memory  14  is where the program execution device  11  stores the above various programs and data copied from the external storage device  13  when the program execution device  11  executes these programs. The working memory  14  is typically made up of a storage medium having a relatively high access speed. For example, a portion of the DRAM memory within the program execution device  11  may be used as the working memory  14 . However, a low speed device, such as a disk drive, a memory card, or magnetic tape, can be used as the working memory  14 .  
         [0030]     The coverage measurement program  15  performs coverage measurement and has a function to count and store the number of times each executive instruction has been executed and calculate the coverage, which is equivalent to the function of known coverage measurement tools.  
         [0031]     The coverage measurement control program  16  controls whether to activate the coverage measurement program  15  at each measurement point. The coverage measurement control program  16  and the measurement condition setting table  18  described later are components unique to the present invention. The present embodiment is characterized in that the coverage measurement program  15  is only activated through the coverage measurement control program  16  under conditions indicated in the measurement condition setting table  18 .  
         [0032]     The coverage measurement control program  16  has a function to determine whether to activate the coverage measurement program  15 , as well as a function to activate the coverage measurement program  15  as necessary. The coverage measurement control program  16  checks data in the measurement record table  17  described later, in the measurement condition setting table  18 , and in the conditional decision results display unit  191  described later to determine whether to activate the coverage measurement program  15 .  
         [0033]     Based on the determination result, the coverage measurement program  16  performs one of the following two operations:  
         [0034]     (a) The coverage measurement program  16  first activates the coverage measurement program  15  so that the coverage measurement program  15  can perform coverage measurement, and then terminates itself.  
         [0035]     (b) The coverage measurement program  16  terminates itself without any processing. No coverage measurement is carried out since the coverage measurement program  16  terminates itself without activating the coverage measurement program  15 .  
         [0036]     The measurement record table  17  is a table in which the coverage measurement control program  16  stores coverage information on the measurement target program  12 . The measurement condition setting table  18  stores conditions under which to obtain coverage information on the measurement target program  12 . As described above, the coverage measurement control program  16  determines whether to activate the coverage measurement program  15  based on data in the measurement record table  17  and in the measurement condition setting table  18 .  
         [0037]     The program execution device  11  also includes a processing results display unit  19 , which is made up of the conditional decision results display unit  191  and a return address display unit  192  (not shown in  FIG. 1 ).  
         [0038]     The conditional decision results display unit  191  is made up of a flip-flop, a register, or a storage area for indicating a conditional decision result. The program execution device  11  performs conditional branch processing, etc. based on the conditional decision result. According to the present embodiment, the conditional decision results display unit  19  continues to display the conditional decision result until the target conditional branch instruction is executed. The display is reset to its initial state only after the conditional branch instruction has been executed. The return address display unit  192  is made up of a register or a storage area for storing the return address from a function call, etc.  
         [0039]     The program execution device  11  stores and runs the measurement point setting program  20  in its memory. The measurement point setting program  20  has a function to process the measurement target program  12  so that the measurement target program  12  can be subjected to coverage measurement unique to the present invention.  
         [0040]     Further, the information processing device  1  also includes components of a general information processing device. In  FIG. 1 , these components are an I/O controller  31 , a display controller  32 , and devices such as a keyboard  310 , a mouse  311 , frame memory  320 , and a display device  321  which are controlled by the controllers. Further, the information processing device  1  is configured such that the component devices are connected to one another through a bus bridge interface controller  30  for data exchange.  
         [0041]      FIG. 2  is a diagram showing the structure of the measurement target program  12  according to the present embodiment.  FIG. 3  shows the original structure of the measurement target program  12  before it is processed for coverage measurement.  FIG. 4  shows an exemplary conventional structure of the measurement target program  12 .  
         [0042]     The measurement target program  12  is made up of a plurality of instruction codes. These instruction codes are not limited to statements of a specific language. For example, they may be of a machine language, an interpreter intermediate language, etc. Alternatively, each instruction code may be a single processing statement of a high-level language such as the C language.  
         [0043]     Referring to  FIG. 2 , the instruction code  4  causes processing to jump to LABEL002 only when a prescribed condition is met (TRUE). When the instruction code  4  is checked, the program execution device  11  determines whether or not to jump by checking the conditional decision results display unit  191 .  
         [0044]     Further, the instruction code  3  in  FIG. 2  causes processing to jump to the code of the coverage measurement control program  16 . That is, execution of the instruction code  3  causes the coverage measurement control program  16  to be activated, which then determines whether the TRUE branch or the FALSE branch of the conditional branch instruction (the instruction code  4 ) immediately succeeding the instruction code  3  will be taken when the instruction is executed, and stores the determination result. The instruction code  3  is added to the original program as shown in  FIG. 3  to measure the coverage of the conditional branches of the instruction code  4 . The instruction code  3  can be a software interrupt instruction. However, the following description assumes it to be a jump instruction, or branch instruction, with a link. A jump instruction with a link causes processing to jump after storing the return address. When processing returns from a function, etc., the stored return address is transferred to the program counter (PC).  
         [0045]     The present embodiment employs the return address display unit  192  to store the return address. Referring to the program shown in  FIG. 2 , upon execution of the instruction code  3  by the program execution device  11 , it stores the location in the return address display unit  192 , i.e., storing the address, of the instruction code  4 , which is subjected to coverage measurement.  
         [0046]     The coverage measurement control program  16  can recognize the instruction code  4  as a measurement target by checking the return address display unit  192 , since the return address display unit  192  stores the address of the measurement target. The coverage measurement control program  16  then determines whether the TRUE branch or FALSE branch of the instruction code  4  will be taken, or whether or not to jump, by checking the conditional decision result (TRUE or FALSE) displayed on the conditional decision results display unit  191 , and stores the determination result.  
         [0047]     After the coverage measurement control program  16  has performed coverage measurement on the instruction code  4 , processing returns to the address indicated by the return address display unit  192 , that is, the address of the instruction code  4 . Then, the program execution device  11  executes the instruction code  4 .  
         [0048]     It should be noted that the measurement point setting program  12  has processed the original measurement target program  12  shown in  FIG. 3  into the measurement target program  12  shown in  FIG. 2 .  
         [0049]     Thus, in known coverage measurement, for example, a jump instruction (instruction code  3 ) for jumping to the coverage measurement program  15  is added to the original measurement target program  12  in  FIG. 3  generated during program compilation or assembly, producing the measurement target program  12  shown in Fig.  FIG. 4 , which is executed by the program execution device  11  to cause the coverage measurement program  15  to perform coverage measurement.  
         [0050]     According to the present embodiment, however, the measurement point setting program  20  processes the measurement target program  12  shown in  FIG. 4  such that the instruction code  3  is replaced by a jump instruction code to the coverage measurement control program  16 . The present embodiment is characterized by this new instruction code  3  for jumping to the coverage measurement control program  16 . Therefore, in the present embodiment, execution of the instruction code  3  causes the coverage measurement control program  16  to be called, whereas in a known conventional coverage measurement system, execution of the instruction code  3  causes the coverage measurement program  15  to be directly called.  
         [0051]      FIG. 5  shows the configuration of the measurement record table  17  according to the present embodiment. This measurement record table is equivalent to that used by known coverage measurement tools. The coverage measurement program  15  uses the measurement record table  17  to store the number of times each executive instruction has been executed, which is referred to in this specification as the “pass count”. In  FIG. 5 , the instruction code  4  shown in  FIG. 2  is registered as being at measurement point  1 .  
         [0052]     The measurement record table  17  is configured such that when the instruction at a measurement point is a conditional branch instruction such as the instruction code  4 , the pass count  171  can be set separately for each of the TRUE and FALSE branches of the conditional branch instruction, as shown in  FIG. 5 . In addition, each record in the measurement record table  17  includes a measurement point number  172 , an address  173 , an instruction code number  174 , and a branch  175 . The address  173  indicates the location of the instruction code  174  at the measurement point  172 . The table shown in  FIG. 5  indicates that the instruction code  4  shown in  FIG. 2  is located at 00010000H. It should be noted that if it is only necessary to indicate whether each branch has ever been taken at least once, the pass count field  171  may store some symbol, instead of a count, representing such information.  
         [0053]     The coverage measurement program  15  updates the pass count fields  1710  and  1711  for the measurement point  1  in the following manner. Assume that the conditional decision results display unit  191  is indicating TRUE and the return address display unit  192  is indicating the address of the instruction code  4 . In such a case, the coverage measurement program  15  increments the numerical value in the field  1710  by one to indicate the number of times the TRUE branch of the instruction code  4  has been taken or the pass count for the TRUE branch. If, on the other hand, the conditional decision results display unit  191  is indicating FALSE, the coverage measurement program  15  increments the value in the field  1711  by one to indicate the number of times the FALSE branch of the instruction code  4  has been taken or the pass count for the FALSE branch. In the above cases, if it is only necessary to indicate whether each branch has ever been taken at least once, the coverage measurement program  15  overwrites the field  1710 , or field  1711 , with some symbol to indicate that the TRUE branch, or the FALSE branch, has been taken.  
         [0054]     The measurement record table  17  in  FIG. 5  shows that the number of times the TRUE branch of the instruction code  4  has been taken or the pass count for the TRUE branch is  1  and the number of times the FALSE branch has been taken or the pass count for the FALSE branch is 0. The C0 and C1 coverages of the portion of the measurement target program  12  shown in  FIG. 2  are calculated based on the above data in the measurement record table  17  as below.  
         [0055]     The number of unexecuted instruction codes is 1 (only the instruction code  5 ) and the number of executed instruction codes is  4  (the instruction codes  1 ,  2 ,  4 , and  6 ).  
         [0056]     Therefore:  
         [0057]     C0 coverage=(number of executed instruction codes)/(total number of instruction codes)=(5-1)/5=80%, and  
         [0058]     C1 coverage=50%.  
         [0059]     On the other hand, if the value in the field  1710 =0 and the value in the field  1711 &gt;0, then there is no unexecuted instruction code.  
         [0060]     Therefore:  
         [0061]     C0 coverage=(5-0)/5=100% and  
         [0062]     C1 coverage=50%.  
         [0063]     It should be noted that the measurement record table  17  is typically generated by a compiler, assembler, etc. when the measurement target program  12  shown in  FIG. 3  is transformed into the measurement target program  12  shown in  FIG. 4 . The present embodiment also generates the measurement record table  17  in such a manner.  
         [0064]      FIG. 6  shows the configuration of the measurement condition setting table  18  according to the present embodiment. The coverage measurement control program  16  checks this table to determine whether to perform coverage measurement.  
         [0065]     The measurement condition setting table  18  is configured such that when the instruction at a measurement point is a conditional branch instruction such as the instruction code  4 , the maximum allowable number of measurements  181  can be set separately for each of the TRUE and FALSE branches of the conditional branch instruction, as shown in  FIG. 6 . In addition, each record in the measurement condition setting table  18  includes a measurement point number  172 , an address  173 , an instruction code number  174 , and a branch  175 . The address  173  indicates the location of the instruction code  174  at the measurement point  172 . The table shown in  FIG. 6  indicates that the instruction code  4  shown in  FIG. 2  is located at 00010000H.  
         [0066]     The “maximum allowable number of measurements” field  181  typically stores the maximum allowable number of measurements set for each measurement point. In the case of the measurement point  1  shown in  FIG. 6 , the maximum allowable number of measurements is set at “1” for each of the TRUE and FALSE branches of the instruction. If no maximum is to be placed on the allowable number of measurements at each measurement point, a value (e.g., −1) indicating that there is no maximum limit is stored in the “maximum allowable number of measurements” field  181 .  
         [0067]     The repeated-measurement-at-all-points flag  186  is set to ON when coverage measurement is to be repeatedly performed at all measurement points. That is, when this flag is set to ON, the present embodiment performs the same operation as known coverage measurement tools.  
         [0068]     It should be noted that when the maximum allowable number of measurements  181  at each measurement point is 1, there is no need for the “maximum allowable number of measurements” field  181  and hence the measurement condition setting table  18  itself.  
         [0069]     A description will be given below of the processing operation of the present embodiment configured as shown in FIGS.  1  to  6 .  
         [0070]     First, a description will be given of the operation performed when no maximum is placed on the allowable number of measurements at each measurement point, which is achieved by setting the repeated-measurement-at-all-points flag  186  in the measurement condition setting table  18  to ON. In this operation, the program execution device  11  executes the instruction code  3 , as in known coverage measurement operation.  
         [0071]     Immediately after the program execution device  11  executes the instruction code  3  shown in  FIG. 2 , the coverage measurement control program  16  takes control. The coverage measurement control program  16  checks the repeated-measurement-at-all-points flag  186  in the measurement condition setting table  18 . Upon determining that the repeated-measurement-at-all-points flag  186  is set to ON, the coverage measurement control program  16  activates the coverage measurement program  15 . The activated coverage measurement program  15  performs processing for predetermined known coverage measurement.  
         [0072]     An exemplary initial step in conducting the predetermined coverage measurement is to update the pass count. Specifically, the coverage measurement program  15  updates (increments) the pass count field  171  in the measurement record table  17 . For example, assume that the conditional decision results display unit  191  is indicating TRUE and the return address display unit  192  is indicating the address of the instruction code  4 . In such a case, the coverage measurement program  15  increments the numerical value in the field  1710  by one to indicate the number of times the TRUE branch of the instruction code  4  has been taken. If, on the other hand, the conditional decision results display  191  is indicating FALSE, the coverage measurement program  15  increments the value in the field  1711  by one to indicate the number of times the FALSE branch of the instruction code  4  has been taken. If it is only necessary to indicate whether each branch has ever been taken at least once, the coverage measurement program  15  overwrites the field  1710 , or field  1711 , with some symbol instead of incrementing the numerical value to indicate that the TRUE branch, or the FALSE branch has been taken.  
         [0073]     The coverage measurement program  15  then calculates the C0 and C1 coverages based on the pass count data before ending this step. The C0 and C1 coverages are obtained as below.  
         [0074]     For example, when the value in the field  1710 &gt;0 and the value in the field  1711 =0, the number of unexecuted instruction codes is 1 (only the instruction code  5 ) and the number of executed instruction codes is 4 (the instruction codes  1 ,  2 ,  4 , and  6 ).  
         [0075]     Therefore:  
         [0076]     C0 coverage=(number of executed instruction codes)/(total number of instruction codes)=(5-1)/5=80%, and  
         [0077]     C1 coverage=50%.  
         [0078]     On the other hand, when the value in the field  1710 =0 and the value in the field  1711 &gt;0, there is no unexecuted instruction code.  
         [0079]     Therefore:  
         [0080]     C0 coverage=(5-0)/5=100%, and  
         [0081]     C1 coverage=50%.  
         [0082]     Upon completion of the processing by the coverage measurement program  15 , the coverage measurement control program  16  takes control and terminates itself immediately. The above series of coverage measurement steps produces results equivalent to those obtained from known coverage measurement steps.  
         [0083]     With reference to  FIG. 7 , a description will be given below of the operation performed when an upper limit is placed on the allowable number of measurements at each measurement point.  FIG. 7  shows an exemplary procedure for performing a coverage measurement control unique to the present embodiment.  
         [0084]     At step  701 , the coverage measurement control program  16  checks the repeated-measurement-at-all-points flag  186  in the measurement condition setting table  18  and determines that the flag is set to OFF. Then, since an upper limit is placed on the allowable number of measurements at each measurement point, instead of performing the known coverage measurement procedure as described above, the coverage measurement control program  16  performs the following processing without immediately activating the coverage measurement program  15 . The following description assumes that the return address display unit  192  is indicating the address 00010000H, and the instruction code  4 , which is the conditional branch instruction to be checked, is located at this address.  
         [0085]     At step  702 , the coverage measurement control program  16  first obtains the decision result stored in the conditional decision results display unit  191  and the return address stored in the return address display unit  192 . The coverage measurement control program  16  determines the obtained return address to be 00010000H and further determines whether the conditional decision result indicates TRUE or FALSE (step  703 ).  
         [0086]     If the conditional decision result indicates TRUE, at steps  704  and  705  the coverage measurement control program  16  accesses both the measurement record table  17  and the measurement condition setting table  18  to read out the pass count  1710  for the TRUE branch of the branch instruction at the measurement point having the above address and the maximum allowable number of measurements  1810  set for the TRUE branch. The coverage measurement control program  16  compares the obtained pass count  1710  and maximum allowable number of measurements  1810  at step  706 . Alternatively, the coverage measurement control program  16  determines whether the pass count field  1710  stores any symbol indicating that the branch was previously taken. Alternatively, if the maximum allowable number of measurements  1810  is decremented by one each time the branch is taken, the coverage measurement control program  16  determines whether the maximum allowable number of measurements  1810  has reached zero.  
         [0087]     If the maximum allowable number of measurements≦the pass count, or if the pass count field stores some symbol indicating that the branch was previously taken, measurement on the TRUE branch at this measurement point need not be carried out. Therefore, the coverage measurement control program  16  does not call the coverage measurement program  15  and terminates itself immediately at step  711  without any further processing.  
         [0088]     If the maximum allowable number of measurements&gt;the pass count, or if the pass count field does not store any symbol indicating that the branch was previously taken, measurement on the TRUE branch at this measurement point need be carried out. Therefore, the coverage measurement control program  16  calls the coverage measurement program  15  before it terminates itself (steps  710  and  711 ).  
         [0089]     On the other hand, if the conditional decision result obtained from the conditional decision results display unit  191  indicates FALSE at step  703 , the coverage measurement control program  16  accesses both the measurement record table  17  and the measurement condition setting table  18  and reads out the pass count  1711  for the FALSE branch of the branch instruction at the measurement point having the above address and the maximum allowable number of measurements  1811  set for the FALSE branch (steps  707  and  708 ). The coverage measurement control program  16  compares the obtained pass count  1711  with the maximum allowable number of measurements  1811  at step  709 . Alternatively, the coverage measurement control program  16  determines whether the pass count field  1711  stores any symbol indicating that the branch was previously taken. Alternatively, if the maximum allowable number of measurements  1811  is decremented by one each time the branch is taken, the coverage measurement control program  16  determines whether the maximum allowable number of measurements  1811  has reached zero.  
         [0090]     If the maximum allowable number of measurements≦the pass count, or if the pass count field stores some symbol indicating that the branch was previously taken, measurement on the FALSE branch at this measurement point need not be carried out. Therefore, the coverage measurement control program  16  does not call the coverage measurement program  15  and terminates itself immediately at step  711  without any further processing.  
         [0091]     If, on the other hand, the maximum allowable number of measurements&gt;the pass count, or if the pass count field does not store any symbol indicating that the branch was previously taken, measurement on the FALSE branch at this measurement point need be carried out. Therefore, the coverage measurement control program  16  calls the coverage measurement program  15  before it terminates itself (steps  710  and  711 ).  
         [0092]     It should be noted that if an interpreter program traces the instruction codes  1 ,  2 ,  4 ,  5 , and  6  shown in  FIG. 2 , it may call the coverage measurement program  16  each time an instruction code is checked. Whether the coverage measurement program  16  calls the coverage measurement program  15  depends on the determination at steps  701  and  706 . In such a case, when checking the instruction codes  1 ,  2 ,  5 , and  6 , the coverage measurement control program  16  skips steps  702  and  703  and then performs steps  704 ,  705 ,  706 , and  710 , since these instructions are not branch instructions. In this case, the instruction code  3  may or may not be inserted into the measurement target program  12 .  
         [0093]     As described above, the present embodiment avoids counting the number of times each branch has been taken, or the pass count of each branch, when the count has reached a predetermined value or the maximum allowable number of measurements. This eliminates unnecessary measurement and thereby reduces measurement overhead.  
         [0094]     It should be noted that the present embodiment maximizes the function of the coverage measurement program  15 , which is a known coverage measurement program, allowing the coverage measurement program  15  to perform processing such as calculating coverage after measuring pass counts and associating each processing statement of high-level language code with obtained pass count data.  
         [0095]     That is, the coverage measurement program  15  performs known coverage calculation processing using pass count data obtained as described above.  
         [0096]     Further, when each instruction code of the measurement target program  12  is generated using high-level language codes through a language processor such as a compiler, the known coverage measurement program  15  may generate information for associating each processing statement in the high-level language code with the pass count data, as well as calculating the coverage, if the coverage measurement program  15  has such a function.  
         [0097]     As a result, the coverage measurement control program  16 , which is unique to the present embodiment, can be realized by compact processing and hence can be implemented at reduced cost.  
         [0098]     According to the present embodiment described above, the measurement record table  17  is accessed by both the coverage measurement program  15  and the coverage measurement control program  16 . However, a table equivalent to the measurement record table  17  may be provided and dedicated to the coverage measurement control program  16  separately from the measurement record table  17 .  
         [0099]     Further, the measurement record table  17  and the measurement condition setting table  18  employed by the present embodiment described above may be combined into a single table since they store duplicate data. Further, the measurement record table  17  may be omitted if the pass count field  171  is not provided and the value in the “maximum allowable number of measurements” field  181  is decremented by one each time the instruction is executed. Further, the measurement condition setting table  18  may also be omitted if all instructions have their maximum allowable number of measurements  181  set to 1.  
         [0100]     Further according to the present embodiment described above, the program execution device  11  copies various components stored in the external storage device  13  such as a hard disk or the like to its memory or the working memory  14  and then executes or references these components. However, the program execution device  11  may copy these components from an external storage medium such as a CD-ROM or a flexible disk or from semiconductor memory such as flash EEPROM, or other storage media. Further, these components may be externally obtained through data communications and stored in some storage medium. Further, the present invention is not limited to the embodiment described above, and various alterations may be made thereto without departing from the spirit and the scope of the invention.  
         [0101]     The present invention can be applied to any product with built-in software in order to increase the efficiency and accuracy of its development.  
         [0102]     Having described a preferred embodiment of the invention with reference to the accompanying drawings, it is to be understood that the invention is not limited to the embodiment and that various changes and modifications could be effected therein by one skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims.