Add a test for _lpython_str_equal()

Author: certik

integration_tests/run_tests.py

@@ -23,6 +23,7 @@
     "test_builtin_int.py",
     "test_builtin_len.py",
     "test_builtin_float.py",
+    "test_builtin_str_02.py",
     "test_math1.py",
     "test_math_02.py",
     "test_c_interop_01.py",

integration_tests/test_builtin_str_02.py

@@ -0,0 +1,19 @@
+def _lpython_str_equal(a: str, b: str) -> bool:
+    if len(a) != len(b):
+        return False
+    i: i32
+    for i in range(len(a)):
+        if a[i] != b[i]:
+            return False
+    return True
+
+def f():
+    assert _lpython_str_equal("a", "a")
+    assert not _lpython_str_equal("a2", "a")
+    assert not _lpython_str_equal("a", "a123")
+    assert not _lpython_str_equal("a23", "a24")
+    assert _lpython_str_equal("a24", "a24")
+    assert _lpython_str_equal("abcdefg", "abcdefg")
+    assert not _lpython_str_equal("abcdef3", "abcdefg")
+
+f()