Refactor content type check for response handling

src/include-fragment-element.ts

@@ -234,13 +234,13 @@ export class IncludeFragmentElement extends HTMLElement {
     try {
       await this.#task(['loadstart'])
       const response = await this.fetch(this.request())
-      if (response.status !== 200) {
-        throw new Error(`Failed to load resource: the server responded with a status of ${response.status}`)
-      }
       const ct = response.headers.get('Content-Type')
       if (!isWildcard(this.accept) && (!ct || !ct.includes(this.accept ? this.accept : 'text/html'))) {
         throw new Error(`Failed to load resource: expected ${this.accept || 'text/html'} but was ${ct}`)
       }
+      if (response.status !== 200) {
+        throw new Error(`Failed to load resource: the server responded with a status of ${response.status}`)
+      }
 
       const responseText: string = await response.text()
       let data: string | CSPTrustedHTMLToStringable = responseText

test/test.js

@@ -213,7 +213,7 @@ suite('include-fragment-element', function () {
       await el.data
       throw new Error('el.data did not throw')
     } catch (error) {
-      assert.match(error, /the server responded with a status of 406/)
+      assert.match(error, /expected text\/html but was text\/plain/)
     }
   })
 
@@ -343,7 +343,10 @@ suite('include-fragment-element', function () {
     assert.equal(event.bubbles, false)
     assert.equal(event.cancelable, false)
     assert.instanceOf(event.detail.error, Error)
-    assert.equal(event.detail.error.message, 'Failed to load resource: the server responded with a status of 500')
+    assert.equal(
+      event.detail.error.message,
+      'Failed to load resource: expected text/html but was text/plain;charset=UTF-8',
+    )
   })
 
   test('adds is-error class on 500 status', async function () {