Added wait_for_contains_class

Author: Lachlan Teale

dash/testing/browser.py

@@ -26,6 +26,7 @@
     style_to_equal,
     class_to_equal,
     contains_text,
+    contains_class,
     until,
 )
 from dash.testing.dash_page import DashPageMixin
@@ -343,6 +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