test: add --interactive tests to test_emrun

Signed-off-by: Kohei Tokunaga <ktokunaga.mail@gmail.com>

Author: ktock

test/test_browser.py

@@ -5659,6 +5659,7 @@ def test_program_arg_separator(self):
 
   def test_emrun(self):
     self.emcc('test_emrun.c', ['--emrun', '-o', 'test_emrun.html'])
+    self.emcc('test_interactive_emrun.c', ['--emrun', '-pthread', '-sPROXY_TO_PTHREAD', '-sEXIT_RUNTIME', '-o', 'test_interactive_emrun.html'])
     if not has_browser():
       self.skipTest('need a browser')
 
@@ -5697,6 +5698,7 @@ def test_emrun(self):
         ['--private_browsing', '--port', '6941'],
         ['--dump_out_directory', 'other dir/multiple', '--port', '6942'],
         ['--dump_out_directory=foo_bar', '--port', '6942'],
+        ['--interactive'],
     ]:
       args = args_base + args + [self.in_dir('test_emrun.html'), '--', '1', '2', '--3', 'escaped space', 'with_underscore']
       print(shlex.join(args))
@@ -5721,6 +5723,12 @@ def test_emrun(self):
       self.assertContained('Testing char sequences: %20%21 ä', stdout)
       self.assertContained('hello, error stream!', stderr)
 
+    args = args_base + ['--interactive', self.in_dir('test_interactive_emrun.html')]
+    print(shlex.join(args))
+    proc = self.run_process(args, check=False, input="hello")
+    self.assertEqual(proc.returncode, 100)
+    self.assertContained('hello', stdout)
+
 
 class browser64(browser):
   def setUp(self):

test/test_interactive_emrun.c

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2025 The Emscripten Authors.  All rights reserved.
+ * Emscripten is available under two separate licenses, the MIT license and the
+ * University of Illinois/NCSA Open Source License.  Both these licenses can be
+ * found in the LICENSE file.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <sys/select.h>
+#include <stdlib.h>
+
+int main(int argc, char **argv) {
+  fd_set readfds;
+  char buf[124];
+  ssize_t n;
+  int nr = 0;
+
+  while (nr < sizeof(buf)) {
+    FD_ZERO(&readfds);
+    FD_SET(STDIN_FILENO, &readfds);
+    assert(select(STDIN_FILENO + 1, &readfds, NULL, NULL, NULL) == 1);
+    assert(FD_ISSET(STDIN_FILENO, &readfds));
+    n = read(STDIN_FILENO, &(buf[nr]), sizeof(buf) - nr);
+    assert(n >= 0);
+    if (n == 0) break;
+    nr += n;
+  }
+
+  printf("%s\n", buf);
+
+  exit(0);
+}