From a8870ecc937385e5d26b71f4ea27f2410a11e9ff Mon Sep 17 00:00:00 2001
From: Sebastian Aas <sebastian.aas@outlook.com>
Date: Thu, 26 Dec 2024 16:36:35 +0100
Subject: [PATCH] #1007: show diff between expected and actual in test runner

---
 CHANGELOG.md                                |  4 ++-
 src/extension-test/unit/test-runner-test.ts | 31 ++++++++++++++++++++
 src/nrepl/cider.ts                          | 32 +++++++++++++++++++++
 src/testRunner.ts                           |  2 ++
 4 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa5c75dfc..c67d7e2ce 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@ Changes to Calva.
 
 ## [Unreleased]
 
+- Fix: [Have test runner show diff between "actual" and "expected"](https://github.com/BetterThanTomorrow/calva/issues/1007)
+
 ## [2.0.483] - 2025-01-08
 
 - Fix: [Paredit garbles while backspacing rapidly](https://github.com/BetterThanTomorrow/calva/issues/2611)
@@ -12,7 +14,7 @@ Changes to Calva.
 
 ## [2.0.482] - 2024-12-03
 
-- Fix: [Added 'replace-refer-all-with-alias' & 'replace-refer-all-with-refer' actions to calva.](https://github.com/BetterThanTomorrow/calva/issues/2667) 
+- Fix: [Added 'replace-refer-all-with-alias' & 'replace-refer-all-with-refer' actions to calva.](https://github.com/BetterThanTomorrow/calva/issues/2667)
 
 ## [2.0.481] - 2024-10-29
 
diff --git a/src/extension-test/unit/test-runner-test.ts b/src/extension-test/unit/test-runner-test.ts
index 714649f90..3c7a6018b 100644
--- a/src/extension-test/unit/test-runner-test.ts
+++ b/src/extension-test/unit/test-runner-test.ts
@@ -167,4 +167,35 @@ orange`
 apple`
     );
   });
+
+  it('can produce detailed messages with diffs', () => {
+    expect(
+      cider.detailedMessage({
+        type: 'fail',
+        ns: 'core',
+        context: 'ctx',
+        index: 2,
+        expected: '{:key1 "value1", :key2 "value2"}',
+        actual: '{:key1 "wrongValue", :key2 "value2"}',
+        var: 'test',
+        file: 'core.clj',
+        line: 10,
+        message: 'Values do not match',
+        diffs: [
+          [
+            '{:key1 "wrongValue", :key2 "value2"}',
+            ['{:key1 "value1", :key2 "value2"}', '{:key1 "wrongValue"}'],
+          ],
+        ],
+      })
+    ).toBe(`; FAIL in core/test (core.clj:10):
+; ctx: Values do not match
+; expected:
+{:key1 "value1", :key2 "value2"}
+; actual:
+{:key1 "wrongValue", :key2 "value2"}
+; diff:
+- {:key1 "value1", :key2 "value2"}
++ {:key1 "wrongValue"}`);
+  });
 });
diff --git a/src/nrepl/cider.ts b/src/nrepl/cider.ts
index 5c0e23a0c..d29488e79 100644
--- a/src/nrepl/cider.ts
+++ b/src/nrepl/cider.ts
@@ -142,6 +142,33 @@ export function lineInformation(result: TestResult): string {
   return ` (${result.file}:${result.line})`;
 }
 
+function getDiffMessages(result: TestResult): string[] {
+  const diffs = result.diffs;
+  const messages: string[] = [];
+
+  if (!diffs || !Array.isArray(diffs) || diffs.length === 0) {
+    return messages;
+  }
+
+  diffs.forEach((diffPair: [string, [string, string]]) => {
+    if (Array.isArray(diffPair) && diffPair.length === 2) {
+      const [_, [removed, added]] = diffPair;
+
+      if (removed || added) {
+        messages.push('; diff:');
+        messages.push(removed ? `- ${removed}` : '');
+        if (added) {
+          messages.push(`+ ${added}`);
+        }
+      }
+    } else {
+      console.warn('Invalid diff pair format:', diffPair);
+    }
+  });
+
+  return messages;
+}
+
 // Return a detailed message about why a test failed.
 // If the test passed, return the empty string.
 // The message contains "comment" lines that are prepended with ;
@@ -173,6 +200,11 @@ export function detailedMessage(result: TestResult): string | undefined {
     if (result.actual) {
       messages.push(`; actual:\n${result.actual}`);
     }
+
+    const diffMessages = getDiffMessages(result);
+    if (diffMessages.length > 0) {
+      messages.push(...diffMessages);
+    }
   }
   return messages.length > 0 ? messages.join('\n') : undefined;
 }
diff --git a/src/testRunner.ts b/src/testRunner.ts
index a929ca1b9..d71e94d44 100644
--- a/src/testRunner.ts
+++ b/src/testRunner.ts
@@ -139,6 +139,8 @@ async function onTestResult(
         run.errored(assertion, new vscode.TestMessage(cider.shortMessage(result)));
         break;
       case 'fail':
+        run.failed(assertion, new vscode.TestMessage(cider.detailedMessage(result)));
+        break;
       default:
         run.failed(assertion, new vscode.TestMessage(cider.shortMessage(result)));
         break;