feat: throw explaining error when JSDOM HTML template render failed

.changeset/small-rivers-burn.md

@@ -0,0 +1,5 @@
+---
+"@ima/testing-library": minor
+---
+
+Throw an error when JSDOM HTML template render failed. This can be potentially a **BREAKING CHANGE** if your tests are already using a broken HTML template in JSDOM. Until now, you might not have even noticed the problem until you had a test accessing specific context features that required a proper HTML template.

packages/testing-library/src/jest-preset.ts

@@ -24,6 +24,12 @@ const jestConfig: Promise<Config> = (async () => {
     // Some async errors are swallowed by jest, so we need to log them manually and throw a safe error
     console.error(error.stack ?? error);
 
+    if (error.cause) {
+      // eslint-disable-next-line no-console
+      console.log(); // Empty line to avoid stacking with the error above
+      console.error(error.cause.stack ?? error.cause);
+    }
+
     throw new Error(
       'Failed to get IMA response content. Check the error above.'
     );

packages/testing-library/src/server/content.ts

@@ -47,5 +47,18 @@ export async function getIMAResponseContent(): Promise<string> {
     }
   );
 
+  if (response.status !== 200) {
+    throw new Error(
+      `Failed to generate HTML content for JSDOM template (status: ${response.status}).`,
+      {
+        cause:
+          response.error ||
+          new Error(
+            `This should not happen, file an issue with @ima/testing-library if you are seeing this.`
+          ),
+      }
+    );
+  }
+
   return response.content;
 }