WIP: tests/emulator/poke_around: test setting user.shell

tests/emulator/poke_around.py

@@ -52,3 +52,46 @@ def run(d):
     d.ui.press('enter')
     wait_for(d, 'This is Zip')
     screenshot(d, 'zip-is-still-there')
+
+    def change_shell_and_relogin(shell, descr):
+        import base64
+        import time
+        config = ('{pkgs, ...}: {user.shell = %SHELL%; ' +
+                  'system.stateVersion = "24.05";}').replace('%SHELL%', shell)
+        config_base64 = base64.b64encode(config.encode()).decode()
+        d(f'input text "echo {config_base64} | base64 -d > '
+          '~/.config/nixpkgs/nix-on-droid.nix"')
+        d.ui.press('enter')
+        screenshot(d, f'pre-switch-{descr}')
+        d(f'input text "nix-on-droid switch && echo switched  {descr}"')
+        d.ui.press('enter')
+        time.sleep(1)
+        screenshot(d, f'in-switch-{descr}')
+        wait_for(d, f'switched {descr}')
+        screenshot(d, f'post-switch-{descr}')
+        d('input text "exit"')
+        d.ui.press('enter')
+        screenshot(d, f'pre-re-login-{descr}')
+        d.app('com.termux.nix').launch()
+        time.sleep(1)
+        screenshot(d, f'post-re-login-{descr}')
+
+    # change shell: pkgs.fish -> fish
+    change_shell_and_relogin('pkgs.fish', 'bare-fish')
+    wait_for(d, 'Welcome to fish, the friendly interactive shell')
+    screenshot(d, 're-login-done-bare-fish')
+
+    # change shell: "${pkgs.fish}", which is a directory -> fallback
+    change_shell_and_relogin('"${pkgs.fish}"', 'fish-directory')
+    wait_for(d, 'Cannot execute shell ')
+    wait_for(d, 'it is a directory.')
+    wait_for(d,
+             'Unlike nixos you should point `user.shell` to the exact binary.')
+    wait_for(d, 'Falling back to bash.')
+    wait_for(d, 'bash-5.2$')
+    screenshot(d, 're-login-done-shell-dir-fallback')
+
+    # change shell: "${pkgs.fish}/bin/fish" -> fish
+    change_shell_and_relogin('"${pkgs.fish}/bin/fish"', 'fish-bin-fish')
+    wait_for(d, 'Welcome to fish, the friendly interactive shell')
+    screenshot(d, 're-login-done-fish-bin-fish')