diff --git a/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.spec.mjs b/common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.spec.ts
similarity index 100%
rename from common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.spec.mjs
rename to common/predictive-text/unit_tests/in_browser/cases/top-level-lmlayer.spec.ts
diff --git a/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.mjs b/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.ts
similarity index 99%
rename from common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.mjs
rename to common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.ts
index 966ad85f01..bc2ebb551e 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.mjs
+++ b/common/predictive-text/unit_tests/in_browser/cases/worker-dummy-integration.spec.ts
@@ -6,9 +6,9 @@ import { defaultCapabilities } from '../helpers.mjs';
 // Import assertions, even using 'with', aren't yet supported in Firefox's engine.
 // import hazelModel from '@keymanapp/common-test-resources/json/models/future_suggestions/i_got_distracted_by_hazel.json' with { type: 'json' };
 
-/** @type {string} */
-let domain;
+let domain: string;
 
+// Is based on raw JSON.
 let hazelModel;
 
 /*
diff --git a/common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.mjs b/common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.ts
similarity index 99%
rename from common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.mjs
rename to common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.ts
index 8b7eb7760c..00a50434db 100644
--- a/common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.mjs
+++ b/common/predictive-text/unit_tests/in_browser/cases/worker-trie-integration.spec.ts
@@ -6,8 +6,7 @@ import { defaultCapabilities } from '../helpers.mjs';
 // Import assertions, even using 'with', aren't yet supported in Firefox's engine.
 // import hazelModel from '@keymanapp/common-test-resources/json/models/future_suggestions/i_got_distracted_by_hazel.json' with { type: 'json' };
 
-/** @type {string} */
-let domain;
+let domain: string;
 
 /*
  * How to run the worlist
diff --git a/common/predictive-text/unit_tests/in_browser/web-test-runner.config.mjs b/common/predictive-text/unit_tests/in_browser/web-test-runner.config.mjs
index 76343e0901..7a6e26a256 100644
--- a/common/predictive-text/unit_tests/in_browser/web-test-runner.config.mjs
+++ b/common/predictive-text/unit_tests/in_browser/web-test-runner.config.mjs
@@ -1,7 +1,7 @@
 // @ts-check
 import { devices, playwrightLauncher } from '@web/test-runner-playwright';
 import { summaryReporter } from '@web/test-runner';
-import teamcityReporter from '@keymanapp/common-test-resources/test-runner-TC-reporter.mjs';
+import { esbuildPlugin } from '@web/dev-server-esbuild';
 import { fileURLToPath } from 'url';
 import { dirname, resolve } from 'path';
 
@@ -23,7 +23,7 @@ export default {
   concurrency: 1,
   nodeResolve: true,
   files: [
-    '**/*.spec.mjs'
+    '**/*.spec.ts'
   ],
   middleware: [
     // Rewrites short-hand paths for test resources, making them fully relative to the repo root.
@@ -35,6 +35,9 @@ export default {
       return next();
     }
   ],
+  plugins: [
+    esbuildPlugin({ ts: true, target: 'auto'})
+  ],
   reporters: [
     summaryReporter({}), /* local-dev mocha-style */
   ],