Update flaky test and improve documentation.

This relates to #3

main.go

@@ -89,12 +89,16 @@ func (sr *ShellRunner) Start() {
 // AddCommand adds a shell command to be executed with an optional callback.
 // No commands can be added if the runner has been stopped or not yet started.
 // The callback is executed asynchronously after the command has completed.
-// The order of command execution and callback invocation can be expected to be preserved.
+// The order of command execution and callback invocation can be expected to be preserved (maybe?).
 func (sr *ShellRunner) AddCommand(command string, callback func(*CommandResult)) error {
 	cmd, cancel := sr.newShellCommand(command)
 	return sr.AddCmd(cmd, callback, cancel)
 }
 
+// AddCmd adds a pre-configured exec.Cmd to be executed with an optional callback and cancel function.
+// No commands can be added if the runner has been stopped or not yet started.
+// The callback is executed asynchronously after the command has completed.
+// The order of command execution and callback invocation can be expected to be preserved (maybe?).
 func (sr *ShellRunner) AddCmd(cmd *exec.Cmd, callback func(*CommandResult), cancel context.CancelFunc) error {
 	sr.mu.Lock()
 	defer sr.mu.Unlock()

main_test.go

@@ -78,9 +78,6 @@ func TestShellRunnerCallback(t *testing.T) {
 		t.Fatalf("unexpected error adding command: %v", err)
 	}
 
-	// Wait a sec for the worker to pick up the task
-	time.Sleep(TaskStartWait)
-
 	callbackWait.Add(1)
 
 	if err := runner.AddCommand("echo callback b", func(result *tortoise.CommandResult) {
@@ -93,6 +90,9 @@ func TestShellRunnerCallback(t *testing.T) {
 		t.Fatalf("unexpected error adding command: %v", err)
 	}
 
+	// Wait a sec for the worker to pick up the task
+	time.Sleep(TaskStartWait)
+
 	// Timeout waiting for callbacks
 	done := make(chan struct{})
 	go func() {