diff --git a/test/test_editor_base_panel.py b/test/test_editor_base_panel.py
new file mode 100644
index 00000000..538fa524
--- /dev/null
+++ b/test/test_editor_base_panel.py
@@ -0,0 +1,55 @@
+#     zxlive - An interactive tool for the ZX calculus
+#     Copyright (C) 2023 - Aleks Kissinger
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+
+#    http://www.apache.org/licenses/LICENSE-2.0
+
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import pytest
+
+from zxlive.editor_base_panel import string_to_phase
+from fractions import Fraction
+
+
+def test_string_to_phase():
+    # Test empty input clears the phase.
+    assert string_to_phase('', None, 'fraction') == Fraction(0)
+
+    # Test different ways of specifying integer multiples of pi.
+    assert string_to_phase('3', None, 'fraction') == Fraction(3)
+    assert string_to_phase('3pi', None, 'fraction') == Fraction(3)
+    assert string_to_phase('3*pi', None, 'fraction') == Fraction(3)
+    assert string_to_phase('pi*3', None, 'fraction') == Fraction(3)
+
+    # Test different ways of specifying fractions.
+    assert string_to_phase('pi/2', None, 'fraction') == Fraction(1,2)
+    assert string_to_phase('-pi/2', None, 'fraction') == Fraction(-1,2)
+    assert string_to_phase('5/2', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5pi/2', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5*pi/2', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('pi*5/2', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5/2pi', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5/2*pi', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5/pi*2', None, 'fraction') == Fraction(5,2)
+
+    # Test different ways of specifying floats.
+    assert string_to_phase('5.5', None, 'fraction') == Fraction(11,2)
+    assert string_to_phase('5.5pi', None, 'fraction') == Fraction(11,2)
+    assert string_to_phase('25e-1', None, 'fraction') == Fraction(5,2)
+    assert string_to_phase('5.5*pi', None, 'fraction') == Fraction(11,2)
+    assert string_to_phase('pi*5.5', None, 'fraction') == Fraction(11,2)
+
+    # TODO: test complex and polynomial input.
+
+    # Test bad input.
+    with pytest.raises(ValueError):
+        string_to_phase('bad input', None, 'fraction')
diff --git a/zxlive/editor_base_panel.py b/zxlive/editor_base_panel.py
index b46b3f91..e7461741 100644
--- a/zxlive/editor_base_panel.py
+++ b/zxlive/editor_base_panel.py
@@ -1,6 +1,7 @@
 from __future__ import annotations
 
 import copy
+import re
 from enum import Enum
 from fractions import Fraction
 from typing import Callable, Iterator, TypedDict
@@ -161,16 +162,20 @@ def vert_double_clicked(self, v: VT) -> None:
         if graph.type(v) == VertexType.BOUNDARY or vertex_is_w(graph.type(v)):
             return None
 
+        if graph.type(v) == VertexType.Z_BOX:
+            fraction_or_complex = 'complex'
+            prompt = "Enter desired phase value (complex value):"
+        else:
+            fraction_or_complex = 'fraction'
+            prompt = "Enter desired phase value (in units of pi):"
+
         input_, ok = QInputDialog.getText(
-            self, "Input Dialog", "Enter Desired Phase Value:"
+            self, "Change Phase", prompt
         )
         if not ok:
             return None
         try:
-            if graph.type(v) == VertexType.Z_BOX:
-                new_phase = string_to_phase(input_, self._new_var, 'complex')
-            else:
-                new_phase = string_to_phase(input_, self._new_var, 'fraction')
+            new_phase = string_to_phase(input_, self._new_var, fraction_or_complex)
         except ValueError:
             show_error_msg("Wrong Input Type", "Please enter a valid input (e.g. 1/2, 2)")
             return None
@@ -352,7 +357,7 @@ def string_to_phase(string: str, new_var, fraction_or_complex='fraction'):
     try:
         if fraction_or_complex == 'fraction':
             s = string.lower().replace(' ', '')
-            s = s.replace('\u03c0', '').replace('pi', '')
+            s = re.sub('\\*?(pi|\u04c0)\\*?', '', s)
             if '.' in s or 'e' in s:
                 return Fraction(float(s))
             elif '/' in s:
@@ -367,5 +372,7 @@ def string_to_phase(string: str, new_var, fraction_or_complex='fraction'):
         else:
             return complex(string)
     except ValueError:
-        return parse(string, new_var)
-
+        try:
+            return parse(string, new_var)
+        except Exception as e:
+            raise ValueError