Fix and streamline capability handling

src/WebdriverClassicDriver.php

@@ -789,29 +789,22 @@ private function getNormalisedBrowserName(): string
      */
     private function initCapabilities(array $desiredCapabilities): DesiredCapabilities
     {
-        // Build base capabilities
-        $caps = $this->getBrowserSpecificCapabilities() ?? new DesiredCapabilities();
-
-        // Set defaults
-        $defaults = array_merge(
-            self::DEFAULT_CAPABILITIES['default'],
-            self::DEFAULT_CAPABILITIES[$this->getNormalisedBrowserName()] ?? []
-        );
-        foreach ($defaults as $key => $value) {
-            if ($caps->getCapability($key) === null) {
-                $caps->setCapability($key, $value);
-            }
-        }
-
-        // Merge in other requested types
-        foreach ($desiredCapabilities as $key => $value) {
-            $caps->setCapability($key, $value);
+        $capabilities = $this->createBrowserSpecificCapabilities();
+
+        foreach (
+            array_merge(
+                self::DEFAULT_CAPABILITIES['default'],
+                self::DEFAULT_CAPABILITIES[$this->getNormalisedBrowserName()] ?? [],
+                $desiredCapabilities,
+            ) as $capabilityKey => $capabilityValue
+        ) {
+            $capabilities->setCapability($capabilityKey, $capabilityValue);
         }
 
-        return $caps;
+        return $capabilities;
     }
 
-    private function getBrowserSpecificCapabilities(): ?DesiredCapabilities
+    private function createBrowserSpecificCapabilities(): DesiredCapabilities
     {
         switch ($this->getNormalisedBrowserName()) {
             case WebDriverBrowserType::FIREFOX:
@@ -855,7 +848,7 @@ private function getBrowserSpecificCapabilities(): ?DesiredCapabilities
             case WebDriverBrowserType::MOCK:
             case WebDriverBrowserType::IE_HTA:
             default:
-                return null;
+                return new DesiredCapabilities();
         }
     }