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Source file src/testing/cover.go

Documentation: testing

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // Support for test coverage.
     6  
     7  package testing
     8  
     9  import (
    10  	"fmt"
    11  	"os"
    12  	"sync/atomic"
    13  )
    14  
    15  // CoverBlock records the coverage data for a single basic block.
    16  // The fields are 1-indexed, as in an editor: The opening line of
    17  // the file is number 1, for example. Columns are measured
    18  // in bytes.
    19  // NOTE: This struct is internal to the testing infrastructure and may change.
    20  // It is not covered (yet) by the Go 1 compatibility guidelines.
    21  type CoverBlock struct {
    22  	Line0 uint32 // Line number for block start.
    23  	Col0  uint16 // Column number for block start.
    24  	Line1 uint32 // Line number for block end.
    25  	Col1  uint16 // Column number for block end.
    26  	Stmts uint16 // Number of statements included in this block.
    27  }
    28  
    29  var cover Cover
    30  
    31  // Cover records information about test coverage checking.
    32  // NOTE: This struct is internal to the testing infrastructure and may change.
    33  // It is not covered (yet) by the Go 1 compatibility guidelines.
    34  type Cover struct {
    35  	Mode            string
    36  	Counters        map[string][]uint32
    37  	Blocks          map[string][]CoverBlock
    38  	CoveredPackages string
    39  }
    40  
    41  // Coverage reports the current code coverage as a fraction in the range [0, 1].
    42  // If coverage is not enabled, Coverage returns 0.
    43  //
    44  // When running a large set of sequential test cases, checking Coverage after each one
    45  // can be useful for identifying which test cases exercise new code paths.
    46  // It is not a replacement for the reports generated by 'go test -cover' and
    47  // 'go tool cover'.
    48  func Coverage() float64 {
    49  	var n, d int64
    50  	for _, counters := range cover.Counters {
    51  		for i := range counters {
    52  			if atomic.LoadUint32(&counters[i]) > 0 {
    53  				n++
    54  			}
    55  			d++
    56  		}
    57  	}
    58  	if d == 0 {
    59  		return 0
    60  	}
    61  	return float64(n) / float64(d)
    62  }
    63  
    64  // RegisterCover records the coverage data accumulators for the tests.
    65  // NOTE: This function is internal to the testing infrastructure and may change.
    66  // It is not covered (yet) by the Go 1 compatibility guidelines.
    67  func RegisterCover(c Cover) {
    68  	cover = c
    69  }
    70  
    71  // mustBeNil checks the error and, if present, reports it and exits.
    72  func mustBeNil(err error) {
    73  	if err != nil {
    74  		fmt.Fprintf(os.Stderr, "testing: %s\n", err)
    75  		os.Exit(2)
    76  	}
    77  }
    78  
    79  // coverReport reports the coverage percentage and writes a coverage profile if requested.
    80  func coverReport() {
    81  	var f *os.File
    82  	var err error
    83  	if *coverProfile != "" {
    84  		f, err = os.Create(toOutputDir(*coverProfile))
    85  		mustBeNil(err)
    86  		fmt.Fprintf(f, "mode: %s\n", cover.Mode)
    87  		defer func() { mustBeNil(f.Close()) }()
    88  	}
    89  
    90  	var active, total int64
    91  	var count uint32
    92  	for name, counts := range cover.Counters {
    93  		blocks := cover.Blocks[name]
    94  		for i := range counts {
    95  			stmts := int64(blocks[i].Stmts)
    96  			total += stmts
    97  			count = atomic.LoadUint32(&counts[i]) // For -mode=atomic.
    98  			if count > 0 {
    99  				active += stmts
   100  			}
   101  			if f != nil {
   102  				_, err := fmt.Fprintf(f, "%s:%d.%d,%d.%d %d %d\n", name,
   103  					blocks[i].Line0, blocks[i].Col0,
   104  					blocks[i].Line1, blocks[i].Col1,
   105  					stmts,
   106  					count)
   107  				mustBeNil(err)
   108  			}
   109  		}
   110  	}
   111  	if total == 0 {
   112  		total = 1
   113  	}
   114  	fmt.Printf("coverage: %.1f%% of statements%s\n", 100*float64(active)/float64(total), cover.CoveredPackages)
   115  }
   116  

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