diff --git a/Libraries/LibJS/Tests/test-common.js b/Libraries/LibJS/Tests/test-common.js
index 4f827b6179..7143984d37 100644
--- a/Libraries/LibJS/Tests/test-common.js
+++ b/Libraries/LibJS/Tests/test-common.js
@@ -63,14 +63,15 @@ class ExpectationError extends Error {
 
         toBe(value) {
             this.__doMatcher(() => {
-                this.__expect(Object.is(this.target, value));
+                this.__expect(Object.is(this.target, value),
+                              () => ("toBe: expected _" + String(value) + "_, got _" + String(this.target) + "_"));
             });
         }
 
         // FIXME: Take a precision argument like jest's toBeCloseTo matcher
         toBeCloseTo(value) {
-            this.__expect(typeof this.target === "number");
-            this.__expect(typeof value === "number");
+            this.__expect(typeof this.target === "number", () => "toBeCloseTo: target not of type number");
+            this.__expect(typeof value === "number", () => "toBeCloseTo: argument not of type number");
 
             this.__doMatcher(() => {
                 this.__expect(Math.abs(this.target - value) < 0.000001);
@@ -78,7 +79,7 @@ class ExpectationError extends Error {
         }
 
         toHaveLength(length) {
-            this.__expect(typeof this.target.length === "number");
+            this.__expect(typeof this.target.length === "number", () => "toHaveLength: target.length not of type number");
 
             this.__doMatcher(() => {
                 this.__expect(Object.is(this.target.length, length));
@@ -120,7 +121,7 @@ class ExpectationError extends Error {
 
         toBeDefined() {
             this.__doMatcher(() => {
-                this.__expect(this.target !== undefined);
+                this.__expect(this.target !== undefined, () => "toBeDefined: target was undefined");
             });
         }
 
@@ -138,13 +139,13 @@ class ExpectationError extends Error {
 
         toBeUndefined() {
             this.__doMatcher(() => {
-                this.__expect(this.target === undefined);
+                this.__expect(this.target === undefined, () => "toBeUndefined: target was not undefined");
             });
         }
 
         toBeNaN() {
             this.__doMatcher(() => {
-                this.__expect(isNaN(this.target));
+                this.__expect(isNaN(this.target), () => ("toBeNaN: target was _" + String(this.target) + "_, not NaN"));
             });
         }
 
@@ -258,9 +259,8 @@ class ExpectationError extends Error {
 
         // jest-extended
         fail(message) {
-            // FIXME: message is currently ignored
             this.__doMatcher(() => {
-                this.__expect(false);
+                this.__expect(false, message);
             });
         }
 
@@ -391,12 +391,17 @@ class ExpectationError extends Error {
                 } catch (e) {
                     if (e.name === "ExpectationError") threw = true;
                 }
-                if (!threw) throw new ExpectationError();
+                if (!threw) throw new ExpectationError("not: test didn't fail");
             }
         }
 
-        __expect(value) {
-            if (value !== true) throw new ExpectationError();
+        __expect(value, details) {
+            if (value !== true) {
+                if (details !== undefined)
+                     throw new ExpectationError(details());
+                else
+                     throw new ExpectationError();
+            }
         }
     }
 
@@ -432,6 +437,7 @@ class ExpectationError extends Error {
         } catch (e) {
             suite[message] = {
                 result: "fail",
+                details: String(e),
             };
         }
     };
diff --git a/Userland/test-js.cpp b/Userland/test-js.cpp
index 2a1dadd6b3..f3821d4c97 100644
--- a/Userland/test-js.cpp
+++ b/Userland/test-js.cpp
@@ -52,6 +52,7 @@ enum class TestResult {
 struct JSTest {
     String name;
     TestResult result;
+    String details;
 };
 
 struct JSSuite {
@@ -281,7 +282,7 @@ JSFileResult TestRunner::run_file_test(const String& test_path)
         ASSERT(suite_value.is_object());
 
         suite_value.as_object().for_each_member([&](const String& test_name, const JsonValue& test_value) {
-            JSTest test { test_name, TestResult::Fail };
+            JSTest test { test_name, TestResult::Fail, "" };
 
             ASSERT(test_value.is_object());
             ASSERT(test_value.as_object().has("result"));
@@ -296,6 +297,10 @@ JSFileResult TestRunner::run_file_test(const String& test_path)
                 test.result = TestResult::Fail;
                 m_counts.tests_failed++;
                 suite.most_severe_test_result = TestResult::Fail;
+                ASSERT(test_value.as_object().has("details"));
+                auto details = test_value.as_object().get("details");
+                ASSERT(result.is_string());
+                test.details = details.as_string();
             } else {
                 test.result = TestResult::Skip;
                 if (suite.most_severe_test_result == TestResult::Pass)
@@ -476,7 +481,8 @@ void TestRunner::print_file_result(const JSFileResult& file_result) const
                 printf("         Test:   ");
                 if (test.result == TestResult::Fail) {
                     print_modifiers({ CLEAR, FG_RED });
-                    printf("%s (failed)\n", test.name.characters());
+                    printf("%s (failed):\n", test.name.characters());
+                    printf("                 %s\n", test.details.characters());
                 } else {
                     print_modifiers({ CLEAR, FG_ORANGE });
                     printf("%s (skipped)\n", test.name.characters());