testing: add -test.count flag to run tests and benchmarks multiple times

The flag is available from the go test command as -count:

% go test -run XXX -bench . -count 3
PASS
BenchmarkSprintfEmpty      	30000000	        54.0 ns/op
BenchmarkSprintfEmpty      	30000000	        51.9 ns/op
BenchmarkSprintfEmpty      	30000000	        53.8 ns/op
BenchmarkSprintfString     	10000000	       238 ns/op
BenchmarkSprintfString     	10000000	       239 ns/op
BenchmarkSprintfString     	10000000	       234 ns/op
BenchmarkSprintfInt        	10000000	       232 ns/op
BenchmarkSprintfInt        	10000000	       226 ns/op
BenchmarkSprintfInt        	10000000	       225 ns/op
...

If -cpu is set, each test is run n times for each cpu value.

Original by r (CL 10663).

Change-Id: If3dfbdf21698952daac9249b5dbca66f5301e91b
Reviewed-on: https://go-review.googlesource.com/10669
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/src/testing/testing.go b/src/testing/testing.go
index 2a1c45f768..f64629fe53 100644
--- a/src/testing/testing.go
+++ b/src/testing/testing.go
@@ -172,6 +172,7 @@ var (
 
 	// Report as tests are run; default is silent for success.
 	chatty           = flag.Bool("test.v", false, "verbose: print additional output")
+	count            = flag.Uint("test.count", 1, "run tests and benchmarks `n` times")
 	coverProfile     = flag.String("test.coverprofile", "", "write a coverage profile to the named file after execution")
 	match            = flag.String("test.run", "", "regular expression to select tests and examples to run")
 	memProfile       = flag.String("test.memprofile", "", "write a memory profile to the named file after execution")
@@ -724,9 +725,13 @@ func parseCpuList() {
 			fmt.Fprintf(os.Stderr, "testing: invalid value %q for -test.cpu\n", val)
 			os.Exit(1)
 		}
-		cpuList = append(cpuList, cpu)
+		for i := uint(0); i < *count; i++ {
+			cpuList = append(cpuList, cpu)
+		}
 	}
 	if cpuList == nil {
-		cpuList = append(cpuList, runtime.GOMAXPROCS(-1))
+		for i := uint(0); i < *count; i++ {
+			cpuList = append(cpuList, runtime.GOMAXPROCS(-1))
+		}
 	}
 }