Wait for class testing utilities

CHANGELOG.md

@@ -10,6 +10,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 [#2003](https://github.com/plotly/dash/issues/2003) in which 
 `dangerously_allow_html=True` + `mathjax=True` works in some cases, and in some cases not.
 
+- [#2049](https://github.com/plotly/dash/pull/2043) Added `wait_for_class_to_equal` and `wait_for_contains_class` methods to `dash.testing`
+
+
 ## [2.4.1] - 2022-05-11
 
 ### Fixed

dash/testing/browser.py

@@ -21,7 +21,14 @@
     MoveTargetOutOfBoundsException,
 )
 
-from dash.testing.wait import text_to_equal, style_to_equal, contains_text, until
+from dash.testing.wait import (
+    text_to_equal,
+    style_to_equal,
+    class_to_equal,
+    contains_text,
+    contains_class,
+    until,
+)
 from dash.testing.dash_page import DashPageMixin
 from dash.testing.errors import DashAppLoadingError, BrowserError, TestingTimeoutError
 from dash.testing.consts import SELENIUM_GRID_DEFAULT
@@ -301,6 +308,17 @@ def wait_for_element_by_id(self, element_id, timeout=None):
             f"timeout {timeout or self._wait_timeout}s => waiting for element id {element_id}",
         )
 
+    def wait_for_class_to_equal(self, selector, classname, timeout=None):
+        """Explicit wait until the element's class has expected `value` timeout
+        if not set, equals to the fixture's `wait_timeout` shortcut to
+        `WebDriverWait` with customized `class_to_equal` condition."""
+        return self._wait_for(
+            method=class_to_equal,
+            args=(selector, classname),
+            timeout=timeout,
+            msg=f"classname => {classname} not found within {timeout or self._wait_timeout}s",
+        )
+
     def wait_for_style_to_equal(self, selector, style, val, timeout=None):
         """Explicit wait until the element's style has expected `value` timeout
         if not set, equals to the fixture's `wait_timeout` shortcut to
@@ -326,6 +344,20 @@ def wait_for_text_to_equal(self, selector, text, timeout=None):
             msg=f"text -> {text} not found within {timeout or self._wait_timeout}s",
         )
 
+    def wait_for_contains_class(self, selector, classname, timeout=None):
+        """Explicit wait until the element's classes contains the expected `classname`.
+
+        timeout if not set, equals to the fixture's `wait_timeout`
+        shortcut to `WebDriverWait` with customized `contains_class`
+        condition.
+        """
+        return self._wait_for(
+            method=contains_class,
+            args=(selector, classname),
+            timeout=timeout,
+            msg=f"classname -> {classname} not found inside element within {timeout or self._wait_timeout}s",
+        )
+
     def wait_for_contains_text(self, selector, text, timeout=None):
         """Explicit wait until the element's text contains the expected `text`.
 

dash/testing/wait.py

@@ -68,6 +68,23 @@ def __call__(self, driver):
             return False
 
 
+class contains_class:
+    def __init__(self, selector, classname):
+        self.selector = selector
+        self.classname = classname
+
+    def __call__(self, driver):
+        try:
+            elem = driver.find_element(By.CSS_SELECTOR, self.selector)
+            classname = elem.get_attribute("class")
+            logger.debug(
+                "contains class {%s} => expected %s", classname, self.classname
+            )
+            return self.classname in str(classname)
+        except WebDriverException:
+            return False
+
+
 class text_to_equal:
     def __init__(self, selector, text):
         self.selector = selector
@@ -99,3 +116,20 @@ def __call__(self, driver):
             return val == self.val
         except WebDriverException:
             return False
+
+
+class class_to_equal:
+    def __init__(self, selector, classname):
+        self.selector = selector
+        self.classname = classname
+
+    def __call__(self, driver):
+        try:
+            elem = driver.find_element(By.CSS_SELECTOR, self.selector)
+            classname = elem.get_attribute("class")
+            logger.debug(
+                "class to equal {%s} => expected %s", classname, self.classname
+            )
+            return str(classname) == self.classname
+        except WebDriverException:
+            return False