testing: allow testing of commands that expect stdin

cli/src/ui.rs

@@ -329,8 +329,15 @@ impl Ui {
         }
     }
 
+    pub fn can_prompt() -> bool {
+        io::stdout().is_terminal()
+            || env::var("JJ_INTERACTIVE")
+                .map(|v| v == "1")
+                .unwrap_or(false)
+    }
+
     pub fn prompt(&mut self, prompt: &str) -> io::Result<String> {
-        if !io::stdout().is_terminal() {
+        if !Self::can_prompt() {
             return Err(io::Error::new(
                 io::ErrorKind::Unsupported,
                 "Cannot prompt for input since the output is not connected to a terminal",
@@ -360,7 +367,7 @@ impl Ui {
         choices: &[impl AsRef<str>],
         default: Option<&str>,
     ) -> io::Result<String> {
-        if !io::stdout().is_terminal() {
+        if !Self::can_prompt() {
             if let Some(default) = default {
                 // Choose the default automatically without waiting.
                 writeln!(self.stdout(), "{prompt}: {default}")?;

cli/tests/common/mod.rs

@@ -141,15 +141,45 @@ impl TestEnvironment {
         cmd
     }
 
-    /// Run a `jj` command, check that it was successful, and return its
-    /// `(stdout, stderr)`.
-    pub fn jj_cmd_ok(&self, current_dir: &Path, args: &[&str]) -> (String, String) {
-        let assert = self.jj_cmd(current_dir, args).assert().success();
+    pub fn write_stdin(&self, cmd: &mut assert_cmd::Command, stdin: &str) {
+        cmd.env("JJ_INTERACTIVE", "1");
+        cmd.write_stdin(stdin);
+    }
+
+    pub fn jj_cmd_stdin(
+        &self,
+        current_dir: &Path,
+        args: &[&str],
+        stdin: &str,
+    ) -> assert_cmd::Command {
+        let mut cmd = self.jj_cmd(current_dir, args);
+        self.write_stdin(&mut cmd, stdin);
+
+        cmd
+    }
+
+    fn get_ok(&self, mut cmd: assert_cmd::Command) -> (String, String) {
+        let assert = cmd.assert().success();
         let stdout = self.normalize_output(&get_stdout_string(&assert));
         let stderr = self.normalize_output(&get_stderr_string(&assert));
         (stdout, stderr)
     }
 
+    /// Run a `jj` command, check that it was successful, and return its
+    /// `(stdout, stderr)`.
+    pub fn jj_cmd_ok(&self, current_dir: &Path, args: &[&str]) -> (String, String) {
+        self.get_ok(self.jj_cmd(current_dir, args))
+    }
+
+    pub fn jj_cmd_stdin_ok(
+        &self,
+        current_dir: &Path,
+        args: &[&str],
+        stdin: &str,
+    ) -> (String, String) {
+        self.get_ok(self.jj_cmd_stdin(current_dir, args, stdin))
+    }
+
     /// Run a `jj` command, check that it was successful, and return its stdout
     pub fn jj_cmd_success(&self, current_dir: &Path, args: &[&str]) -> String {
         if self.debug_allow_stderr {