fix classes() for svg elements

src/wrappers/wrapper.js

@@ -69,7 +69,9 @@ export default class Wrapper implements BaseWrapper {
    * Returns an Array containing all the classes on the element
    */
   classes (): Array<string> {
-    let classes = this.element.className ? this.element.className.split(' ') : []
+    // works for HTML Element and SVG Element
+    const className = this.element.getAttribute('class')
+    let classes = className ? className.split(' ') : []
     // Handle converting cssmodules identifiers back to the original class name
     if (this.vm && this.vm.$style) {
       const cssModuleIdentifiers = {}

test/specs/wrapper/classes.spec.js

@@ -20,4 +20,12 @@ describeWithShallowAndMount('classes', (mountingMethod) => {
     const wrapper = mountingMethod(ComponentWithCssModules)
     expect(wrapper.classes()).to.eql(['extension', 'color-red'])
   })
+
+  it('returns array of class names for svg element', () => {
+    const compiled = compileToFunctions('<svg class="a-class b-class"><text class="c-class"/></svg>')
+    const wrapper = mountingMethod(compiled)
+    expect(wrapper.classes()).to.contain('a-class')
+    expect(wrapper.classes()).to.contain('b-class')
+    expect(wrapper.find('text').classes()).to.contain('c-class')
+  })
 })