AK+Tests: Add IntrusiveList<T,...>::insert_before(..) method

The insert_before method on AK::InlineLinkedList is used, so in order to
achieve feature parity, we need to implement it for AK::IntrusiveList as
well.

1 files changed, 26 insertions, 0 deletions

diff --git a/Tests/AK/TestIntrusiveList.cpp b/Tests/AK/TestIntrusiveList.cpp
index 84f1d9f2c2..923de96f3e 100644
--- a/Tests/AK/TestIntrusiveList.cpp
+++ b/Tests/AK/TestIntrusiveList.cpp
@@ -33,6 +33,32 @@ TEST_CASE(insert)
     delete list.take_last();
 }
 
+TEST_CASE(insert_before)
+{
+    IntrusiveTestList list;
+    auto two = new IntrusiveTestItem();
+    list.append(*two);
+    auto zero = new IntrusiveTestItem();
+    list.append(*zero);
+    auto one = new IntrusiveTestItem();
+    list.insert_before(*zero, *one);
+
+    EXPECT_EQ(list.first(), two);
+    EXPECT_EQ(list.last(), zero);
+    EXPECT(list.contains(*zero));
+    EXPECT(list.contains(*one));
+    EXPECT(list.contains(*two));
+
+    EXPECT(zero->m_list_node.is_in_list());
+    EXPECT(one->m_list_node.is_in_list());
+    EXPECT(two->m_list_node.is_in_list());
+    EXPECT_EQ(list.size_slow(), 3u);
+
+    while (auto elem = list.take_first()) {
+        delete elem;
+    }
+}
+
 TEST_CASE(enumeration)
 {
     constexpr size_t expected_size = 10;