Implement the 'shared' subcommand for mmutex

mmutex/cmd/mmutex/exclusive_test.go

Index: mmutex/cmd/mmutex/exclusive_test.go
diff --git a/mmutex/cmd/mmutex/exclusive_test.go b/mmutex/cmd/mmutex/exclusive_test.go
index f32e68004cd68d113e3175b646cef2f5b5b4f02f..8f129d1e26cfb6322aae32a7c3cc07b5cdf2edc8 100644
--- a/mmutex/cmd/mmutex/exclusive_test.go
+++ b/mmutex/cmd/mmutex/exclusive_test.go
@@ -28,8 +28,8 @@ import (
 	. "github.com/luci/luci-go/common/testing/assertions"
 )
 
-func TestMain(t *testing.T) {
-	Convey("RunExclusive executes the command", t, func(c C) {
+func TestExclusive(t *testing.T) {
+	Convey("RunExclusive executes the command", t, func() {
 		var tempDir string
 		var err error
 
@@ -41,9 +41,9 @@ func TestMain(t *testing.T) {
 		testFilePath := filepath.Join(tempDir, "test")
 		var command []string
 		if runtime.GOOS == "windows" {
-			command = []string{"cmd", "/c", "copy", "NUL", testFilePath}
+			command = createCommand([]string{"copy", "NUL", testFilePath})
 		} else {
-			command = []string{"touch", testFilePath}
+			command = createCommand([]string{"touch", testFilePath})
 		}
 
 		So(RunExclusive(command, 0, 0), ShouldBeNil)
@@ -52,11 +52,11 @@ func TestMain(t *testing.T) {
 		So(err, ShouldBeNil)
 	})
 
-	Convey("RunExclusive returns error from the command", t, func(c C) {
+	Convey("RunExclusive returns error from the command", t, func() {
 		So(RunExclusive([]string{"nonexistent_command"}, 0, 0), ShouldErrLike, "executable file not found")
 	})
 
-	Convey("RunExclusive times out if lock isn't released", t, func(c C) {
+	Convey("RunExclusive times out if exclusive lock isn't released", t, func() {
 		var handle fslock.Handle
 		var err error
 
@@ -68,7 +68,19 @@ func TestMain(t *testing.T) {
 		So(RunExclusive([]string{"echo", "should_fail"}, 0, 0), ShouldErrLike, "fslock: lock is held")
 	})
 
-	Convey("RunExclusive respects timeout", t, func(c C) {
+	Convey("RunExclusive times out if shared lock isn't released", t, func() {
+		var handle fslock.Handle
+		var err error
+
+		if handle, err = fslock.LockShared(LockFilePath); err != nil {
+			panic(err)
+		}
+		defer handle.Unlock()
+
+		So(RunExclusive(createCommand([]string{"echo", "should_fail"}), 0, 0), ShouldErrLike, "fslock: lock is held")
+	})
+
+	Convey("RunExclusive respects timeout", t, func() {
 		var handle fslock.Handle
 		var err error
 
@@ -78,7 +90,18 @@ func TestMain(t *testing.T) {
 		defer handle.Unlock()
 
 		start := time.Now()
-		RunExclusive([]string{"echo", "should_fail"}, 5*time.Millisecond, 0)
+		RunExclusive(createCommand([]string{"echo", "should_succeed"}), 5*time.Millisecond, 0)
 		So(time.Now(), ShouldHappenOnOrAfter, start.Add(5*time.Millisecond))
 	})
+
+	// TODO(charliea): Add a test to ensure that a drain file is created when RunExclusive() is called.
+
+	// TODO(charliea): Add a test to ensure that RunExclusive() uses the $CHOPS_SERVICE_LOCK environment
+	// variable to determine the directory for the lock and drain files.
+
+	// TODO(charliea): Add a test to ensure that RunExclusive() just acts as a passthrough if
+	// the $CHOPS_SERVICE_LOCK directory isn't set.
+
+	// TODO(charliea): Add a test to ensure that RunExclusive() just acts as a passthrough if
+	// the $CHOPS_SERVICE_LOCK directory doesn't exist.
 }