Structured Testing - McCabe and Associates

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testability, reliability, and maintainability of software, without going into details about the testing technique. Project Leaders and Managers should read through the entire document, but may skim over the details in sections 2 and 5-8. Quality Assurance, Methodology, and Standards professionals may skim the material in sections 1, 2, and 5 to get an overview of the method, then read section 12 to see where it fits into the software lifecycle. The Appendices also provide important information about experience with the method and implementation details for specific languages. 6
2 Cyclomatic Complexity Cyclomatic complexity [MCCABE1] measures the amount of decision logic in a single software module. It is used for two related purposes in the structured testing methodology. First, it gives the number of recommended tests for software. Second, it is used during all phases of the software lifecycle, beginning with design, to keep software reliable, testable, and manageable. Cyclomatic complexity is based entirely on the structure of software’s control flow graph. 2.1 Control flow graphs Control flow graphs describe the logic structure of software modules. A module corresponds to a single function or subroutine in typical languages, has a single entry and exit point, and is able to be used as a design component via a call/return mechanism. This document uses C as the language for examples, and in C a module is a function. Each flow graph consists of nodes and edges. The nodes represent computational statements or expressions, and the edges represent transfer of control between nodes. Each possible execution path of a software module has a corresponding path from the entry to the exit node of the module’s control flow graph. This correspondence is the foundation for the structured testing methodology. As an example, consider the C function in Figure 2-1, which implements Euclid’s algorithm for finding greatest common divisors. The nodes are numbered A0 through A13. The control flow graph is shown in Figure 2-2, in which each node is numbered 0 through 13 and edges are shown by lines connecting the nodes. Node 1 thus represents the decision of the “if” statement with the true outcome at node 2 and the false outcome at the collection node 5. The decision of the “while” loop is represented by node 7, and the upward flow of control to the next iteration is shown by the dashed line from node 10 to node 7. Figure 2-3 shows the path resulting when the module is executed with parameters 4 and 2, as in “euclid(4,2).” Execution begins at node 0, the beginning of the module, and proceeds to node 1, the decision node for the “if” statement. Since the test at node 1 is false, execution transfers directly to node 5, the collection node of the “if” statement, and proceeds to node 6. At node 6, the value of “r” is calculated to be 0, and execution proceeds to node 7, the decision node for the “while” statement. Since the test at node 7 is false, execution transfers out of the loop directly to node 11, 7
Page 1 and 2: NIST Special Publication 500-235 St
Page 3: Abstract The purpose of this docume
Page 7 and 8: CONTENTS Abstract..................
Page 9 and 10: 11 Maintenance ....................
Page 11 and 12: 1 Introduction 1.1 Software testing
Page 13 and 14: used to represent software systems
Page 15: Figure 1-1 shows the dependencies a
Page 19 and 20: Figure 2-2. Control flow graph for
Page 21 and 22: Virtual Edge Figure 2-4. Control fl
Page 23 and 24: 2.4 Example of v(G) and basis paths
Page 25 and 26: than the cyclomatic complexity numb
Page 27 and 28: 3 Examples of Cyclomatic Complexity
Page 29 and 30: Figure 3-3. Control flow graph with
Page 31 and 32: Figure 3-7. Control flow graph with
Page 33 and 34: 4 Simplified Complexity Calculation
Page 35 and 36: In addition to counting predicates
Page 37 and 38: Figure 4-6 shows a C code module wi
Page 39 and 40: 4.3 Use of automated tools The most
Page 41 and 42: 5 Structured Testing Structured tes
Page 43 and 44: Next, with structured testing, test
Page 45 and 46: Figure 5-2. Code for module “coun
Page 47 and 48: that satisfies the structured testi
Page 49: 5.7 Critical software Different typ
Page 52 and 53: First, for every decision in the mo
Page 54 and 55: 6.4 Example of the baseline method
Page 56 and 57: Of the tests in Figure 6-2, the bas
Page 58 and 59: integration testing can be combined
Page 60 and 61: tured testing at the module level r
Page 62 and 63: ule 3 illustrates that a conditiona
Page 64 and 65: 7.5 Integration complexity The inte
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Although a basis set of paths throu
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Figure 7-7 illustrates the structur
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When abstraction works well, it hid
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are objects of a class type, the ex
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ment is to provide evidence that th
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9 Complexity Reduction Although the
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Figure 9-3. Code after removing unn
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There are many situations in which
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show the reengineered functions “
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Figure 9-10.Graph for structured mo
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In addition to the trade-off betwee
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understood code, since the connecti
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tured logic is superimposed on the
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complexity may not be obvious from
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11.4 Reuse of testing information A
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call resolutions based on complexit
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[DAHL] Dahl, O. and E. Dijkstra and
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[MCCABE5] McCabe, T. and A. Watson,
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[WARD] Ward, W., “Software Defect
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A.3 Walsh 96 The propensity to make
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to avoid changing very complex proc
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testing and maintenance. The projec
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The suggested explanation is that o
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A.21 Koshgoftaar et al Koshgoftaar,
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B.1.2 The module Figure B-1 shows t
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dealer’s hand value. Those two va
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The ninth functional test is a win
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B.2 Experimental comparison of stru
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Structured Testing - McCabe and Associates

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