Make cli parsing testable

Author: tygern

cmd/pi/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"time"
 
 	"github.com/tygern/pi/internal/cli"
@@ -10,7 +11,7 @@ import (
 )
 
 func main() {
-	duration, numberOfWorkers := cli.ParseCommandLineArgs()
+	duration, numberOfWorkers := cli.ParseCommandLineArgs(os.Args[1:])
 
 	ctx, cancel := cli.SigtermTimeoutContext(time.Duration(duration) * time.Second)
 	defer cancel()

internal/cli/support.go

@@ -32,10 +32,12 @@ func SigtermTimeoutContext(timeout time.Duration) (context.Context, context.Canc
 	return ctx, cancel
 }
 
-func ParseCommandLineArgs() (duration, numberOfWorkers int) {
-	flag.IntVar(&duration, "d", 20, "execution duration in seconds")
-	flag.IntVar(&numberOfWorkers, "n", runtime.NumCPU(), "number of workers")
-	flag.Parse()
+func ParseCommandLineArgs(arguments []string) (duration, numberOfWorkers int) {
+	flagSet := flag.FlagSet{}
+	flagSet.IntVar(&duration, "d", 20, "execution duration in seconds")
+	flagSet.IntVar(&numberOfWorkers, "n", runtime.NumCPU(), "number of workers")
+	flagSet.Parse(arguments)
+
 	fmt.Printf("Running for %d seconds with %d workers\n", duration, numberOfWorkers)
 	return duration, numberOfWorkers
 }

internal/cli/support_test.go

@@ -7,8 +7,23 @@ import (
 	"github.com/tygern/pi/internal/cli"
 )
 
+func TestParseCommandLineArgs(t *testing.T) {
+	duration, numberOfWorkers := cli.ParseCommandLineArgs([]string{"-d", "30", "-n", "15"})
+	assert.Equal(t, 30, duration)
+	assert.Equal(t, 15, numberOfWorkers)
+
+	defaultDuration, defaultNumberOfWorkers := cli.ParseCommandLineArgs([]string{})
+	assert.Equal(t, 20, defaultDuration)
+	assert.GreaterThanOrEqualTo(t, defaultNumberOfWorkers, 1)
+}
+
 func TestPrettyPrint(t *testing.T) {
 	assert.Equal(t, "2,300", cli.PrettyPrint(2300))
 	assert.Equal(t, "22,300", cli.PrettyPrint(22300))
 	assert.Equal(t, "222,300", cli.PrettyPrint(222300))
 }
+
+func TestReport(t *testing.T) {
+	assert.Equal(t, "π ≈ 3.141592600000 (10,000,000 iterations)", cli.Report(3.1415926, 10_000_000))
+	assert.Equal(t, "π ≈ 3.000000000000 (4 iterations)", cli.Report(3, 4))
+}