From 8813fba7e131f159915675ca846b2554d3e902cb Mon Sep 17 00:00:00 2001
From: Johannes Kalmbach <johannes.kalmbach@gmail.com>
Date: Wed, 15 Jan 2025 10:18:17 +0100
Subject: [PATCH] Add a unit tests.

Signed-off-by: Johannes Kalmbach <johannes.kalmbach@gmail.com>
---
 test/EngineTest.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/test/EngineTest.cpp b/test/EngineTest.cpp
index e6fcc1e76f..860fa5521e 100644
--- a/test/EngineTest.cpp
+++ b/test/EngineTest.cpp
@@ -278,6 +278,18 @@ TEST(OptionalJoin, specialOptionalJoinTwoColumns) {
     IdTable expectedResult = makeIdTableFromVector(
         {{4, 1, 2, U}, {2, 1, 3, 3}, {1, 1, 4, U}, {2, 2, 2, 4}, {1, 3, 1, 1}});
 
+    testOptionalJoin(a, b, jcls, expectedResult);
+  }
+  {
+    // Test a corner case that previously contained a bug.
+    IdTable a{makeIdTableFromVector({{4, U, 2}})};
+    IdTable b{makeIdTableFromVector({{3, 3, 1}})};
+    // Join a and b on the column pairs 1,2 and 2,1 (entries from columns 1 of
+    // a have to equal those of column 2 of b and vice versa).
+    JoinColumns jcls{{1, 2}, {2, 1}};
+
+    IdTable expectedResult = makeIdTableFromVector({{4, U, 2, U}});
+
     testOptionalJoin(a, b, jcls, expectedResult);
   }
 }