diff --git a/spyder_kernels/utils/tests/test_dochelpers.py b/spyder_kernels/utils/tests/test_dochelpers.py
index 220db9e2..0a2ef240 100644
--- a/spyder_kernels/utils/tests/test_dochelpers.py
+++ b/spyder_kernels/utils/tests/test_dochelpers.py
@@ -18,8 +18,14 @@
 import pytest
 
 # Local imports
-from spyder_kernels.utils.dochelpers import (getargtxt, getdoc, getobj,
-                                             isdefined)
+from spyder_kernels.utils.dochelpers import (
+    getargtxt,
+    getargspecfromtext,
+    getdoc,
+    getobj,
+    getsignaturefromtext,
+    isdefined,
+)
 from spyder_kernels.py3compat import PY2
 
 
@@ -60,5 +66,83 @@ def test_dochelpers():
     assert getobj('4.') == '4'
 
 
+@pytest.mark.skipif(PY2, reason="Fails in Python 2")
+def test_no_signature():
+    """
+    Test that we can get documentation for objects for which Python can't get a
+    signature directly because it gives an error.
+
+    This is a regression test for issue spyder-ide/spyder#21148
+    """
+    import numpy as np
+    doc = getdoc(np.where)
+    signature = doc['argspec']
+    assert signature and signature != "(...)" and signature.startswith("(")
+    assert doc['docstring']
+
+
+@pytest.mark.parametrize(
+    'text, name, expected',
+    [
+         ('foo(x, y)', 'foo', '(x, y)'),
+         ('foo(x, y)', '', '(x, y)'),
+    ]
+)
+def test_getsignaturefromtext_py2(text, name, expected):
+    assert getsignaturefromtext(text, name) == expected
+
+
+@pytest.mark.skipif(PY2, reason="Don't work in Python 2")
+@pytest.mark.parametrize(
+    'text, name, expected',
+    [
+         # Simple text with and without name
+         ('foo(x, y)', 'foo', '(x, y)'),
+         ('foo(x, y)', '', '(x, y)'),
+         # Single arg
+         ('foo(x)', '', '(x)'),
+         ('foo(x = {})', '', '(x = {})'),
+         # Not a valid identifier
+         ('1a(x, y)', '', ''),
+         # Valid identifier
+         ('a1(x, y=2)', '', '(x, y=2)'),
+         # Unicode identifier with and without name
+         ('ΣΔ(x, y)', 'ΣΔ', '(x, y)'),
+         ('ΣΔ(x, y)', '', '(x, y)'),
+         # Multiple signatures in a single line
+         ('ΣΔ(x, y) foo(a, b)', '', '(x, y)'),
+         ('1a(x, y) foo(a, b)', '', '(a, b)'),
+         # Multiple signatures in multiple lines
+         ('foo(a, b = 1)\n\nΣΔ(x, y=2)', '', '(a, b = 1)'),
+         ('1a(a, b = 1)\n\nΣΔ(x, y=2)', '', '(x, y=2)'),
+         # Signature after math operations
+         ('2(3 + 5) 3*(99) ΣΔ(x, y)', '', '(x, y)'),
+         # No identifier
+         ('(x, y)', '', ''),
+         ('foo (a=1, b = 2)', '', ''),
+         # Empty signature
+         ('foo()', '', ''),
+         ('foo()', 'foo', ''),
+    ]
+)
+def test_getsignaturefromtext(text, name, expected):
+    assert getsignaturefromtext(text, name) == expected
+
+
+def test_multisignature():
+    """
+    Test that we can get at least one signature from an object with multiple
+    ones declared in its docstring.
+    """
+    def foo():
+        """
+        foo(x, y) foo(a, b)
+        foo(c, d)
+        """
+
+    signature = getargspecfromtext(foo.__doc__)
+    assert signature == "(x, y)"
+
+
 if __name__ == "__main__":
     pytest.main()