Test and update the wizard module (#466)

Issue #343 is also fixed in this commit. 
The issue caused from when the accordion widget has all steps folder, the selected_index can be `None`, when the status of a step widget is reset, it triggers a widget update and hits at the exception.

aiidalab_widgets_base/wizard.py

@@ -4,12 +4,12 @@
 
     * Carl Simon Adorf <[email protected]>
 """
-from enum import Enum
-from threading import Thread
-from time import sleep, time
+import enum
+import threading
+import time
 
 import ipywidgets as ipw
-import traitlets
+import traitlets as tl
 
 
 class AtLeastTwoStepsWizardError(ValueError):
@@ -21,10 +21,10 @@ def __init__(self, steps):
         )
 
 
-class WizardAppWidgetStep(traitlets.HasTraits):
+class WizardAppWidgetStep(tl.HasTraits):
     "One step of a WizardAppWidget."
 
-    class State(Enum):
+    class State(enum.Enum):
         """Each step is always in one specific state.
 
         The state is used to determine:
@@ -68,8 +68,8 @@ class State(Enum):
         # All error states have negative codes
         FAIL = -1  # the step has unrecoverably failed
 
-    state = traitlets.UseEnum(State)
-    auto_advance = traitlets.Bool()
+    state = tl.UseEnum(State)
+    auto_advance = tl.Bool()
 
     def can_reset(self):
         return hasattr(self, "reset")
@@ -90,13 +90,13 @@ class WizardAppWidget(ipw.VBox):
     @classmethod
     def icons(cls):
         """Return the icon set and return animated icons based on the current time stamp."""
-        t = time()
+        t = time.time()
         return {
             key: item if isinstance(item, str) else item[int(t * len(item) % len(item))]
             for key, item in cls.ICONS.items()
         }
 
-    selected_index = traitlets.Int(allow_none=True)
+    selected_index = tl.Int(allow_none=True)
 
     def __init__(self, steps, **kwargs):
         # The number of steps must be greater than one
@@ -116,12 +116,14 @@ def __init__(self, steps, **kwargs):
 
         # Automatically update titles to implement the "spinner"
 
+        self._run_update_thread = True
+
         def spinner_thread():
-            while True:
-                sleep(0.1)
+            while self._run_update_thread:
+                time.sleep(0.1)
                 self._update_titles()
 
-        Thread(target=spinner_thread).start()
+        threading.Thread(target=spinner_thread).start()
 
         # Watch for changes to each step's state
         for widget in widgets:
@@ -178,6 +180,8 @@ def _consider_auto_advance(self, _=None):
         This is performed whenever the current step is within the SUCCESS state and has
         the auto_advance attribute set to True.
         """
+        if self.accordion.selected_index is None:  # All children are hidden
+            return
 
         with self.hold_trait_notifications():
             index = self.accordion.selected_index
@@ -196,7 +200,7 @@ def _update_step_state(self, _):
             self._update_buttons()
             self._consider_auto_advance()
 
-    @traitlets.observe("selected_index")
+    @tl.observe("selected_index")
     def _observe_selected_index(self, change):
         "Activate/deactivate the next-button based on which step is selected."
         self._update_buttons()

tests/test_wizard.py

@@ -0,0 +1,89 @@
+import ipywidgets as ipw
+import traitlets as tl
+
+
+def test_wizard_app_widget():
+    from aiidalab_widgets_base import WizardAppWidget, WizardAppWidgetStep
+
+    class Step1(ipw.HBox, WizardAppWidgetStep):
+        config = tl.Bool()
+
+        def __init__(self, **kwargs):
+            self.order_button = ipw.Button(description="Submit order", disabled=False)
+            self.order_button.on_click(self.submit_order)
+            super().__init__(children=[self.order_button], **kwargs)
+
+        def submit_order(self, _=None):
+            self.config = True
+
+        @tl.default("config")
+        def _default_config(self):
+            return False
+
+        def reset(self):
+            self.config = False
+
+        @tl.observe("config")
+        def _observe_config(self, _=None):
+            self.state = self.State.SUCCESS if self.config else self.State.INIT
+
+    class Step2(ipw.HBox, WizardAppWidgetStep):
+        config = tl.Bool()
+
+        def __init__(self, **kwargs):
+            self.results = ipw.HTML("Results")
+            super().__init__(children=[self.results], **kwargs)
+
+        def submit_order(self, _=None):
+            pass
+
+        @tl.default("config")
+        def _default_config(self):
+            return False
+
+        @tl.observe("config")
+        def _observe_config(self, change):
+            if self.config:
+                self.state = self.State.READY
+            else:
+                self.state = self.State.INIT
+
+    s1 = Step1(auto_advance=True)
+    s2 = Step2(auto_advance=True)
+    tl.dlink((s1, "config"), (s2, "config"))
+
+    widget = WizardAppWidget(
+        steps=[
+            ("Setup", s1),
+            ("View results", s2),
+        ],
+        testing=True,
+    )
+
+    # Check initial state.
+    assert s1.state == s1.State.INIT
+    assert s2.state == s2.State.INIT
+    assert widget.accordion.selected_index == 0
+
+    s1.order_button.click()
+
+    # Check state after finishing the first step.
+    assert s1.state == s1.State.SUCCESS
+    assert s2.state == s2.State.READY
+    assert widget.accordion.selected_index == 1
+    assert widget.next_button.disabled is True
+
+    # Check state after resetting the app.
+    widget.reset()
+    assert s1.state == s1.State.INIT
+    assert s2.state == s2.State.INIT
+    assert widget.back_button.disabled is True
+
+    # Check state after finishing the first step again.
+    s1.order_button.click()
+    assert s1.state == s1.State.SUCCESS
+    widget.accordion.selected_index = None  # All steps are closed.
+    s1.config = False  # This should trigger an attempt to advance to the next step.
+
+    # Stop the thread that is running the header update to let pytest finish.
+    widget._run_update_thread = False