diff --git a/Tests/AK/CMakeLists.txt b/Tests/AK/CMakeLists.txt
index 5f2b371495..8ac2f2d60e 100644
--- a/Tests/AK/CMakeLists.txt
+++ b/Tests/AK/CMakeLists.txt
@@ -31,6 +31,7 @@ set(AK_TEST_SOURCES
     TestIntrusiveList.cpp
     TestIntrusiveRedBlackTree.cpp
     TestJSON.cpp
+    TestLEB128.cpp
     TestLexicalPath.cpp
     TestMACAddress.cpp
     TestMemMem.cpp
diff --git a/Tests/AK/TestLEB128.cpp b/Tests/AK/TestLEB128.cpp
new file mode 100644
index 0000000000..615b3498af
--- /dev/null
+++ b/Tests/AK/TestLEB128.cpp
@@ -0,0 +1,115 @@
+/*
+ * Copyright (c) 2021, Andrew Kaster <akaster@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/LEB128.h>
+#include <AK/MemoryStream.h>
+#include <LibTest/TestCase.h>
+
+TEST_CASE(single_byte)
+{
+    u32 output = {};
+    i32 output_signed = {};
+    u8 buf[] = { 0x00 };
+    InputMemoryStream stream({ buf, sizeof(buf) });
+
+    // less than/eq 0b0011_1111, signed == unsigned == raw byte
+    for (u8 i = 0u; i <= 0x3F; ++i) {
+        buf[0] = i;
+
+        stream.seek(0);
+        EXPECT(LEB128::read_unsigned(stream, output));
+        EXPECT_EQ(output, i);
+        EXPECT(!stream.handle_any_error());
+
+        stream.seek(0);
+        EXPECT(LEB128::read_signed(stream, output_signed));
+        EXPECT_EQ(output_signed, i);
+        EXPECT(!stream.handle_any_error());
+    }
+
+    // 0b0100_0000 to 0b0111_1111 unsigned == byte, signed = {{ 26'b(-1), 6'b(byte) }}
+    for (u8 i = 0x40u; i < 0x80; ++i) {
+        buf[0] = i;
+
+        stream.seek(0);
+        EXPECT(LEB128::read_unsigned(stream, output));
+        EXPECT_EQ(output, i);
+        EXPECT(!stream.handle_any_error());
+
+        stream.seek(0);
+        EXPECT(LEB128::read_signed(stream, output_signed));
+        EXPECT_EQ(output_signed, (i | (-1 & (~0x3F))));
+        EXPECT(!stream.handle_any_error());
+    }
+    // MSB set, but input too short
+    for (u16 i = 0x80; i <= 0xFF; ++i) {
+        buf[0] = static_cast<u8>(i);
+
+        stream.seek(0);
+        EXPECT(!LEB128::read_unsigned(stream, output));
+        EXPECT(stream.handle_any_error());
+
+        stream.seek(0);
+        EXPECT(!LEB128::read_signed(stream, output_signed));
+        EXPECT(stream.handle_any_error());
+    }
+}
+
+TEST_CASE(two_bytes)
+{
+    u32 output = {};
+    i32 output_signed = {};
+    u8 buf[] = { 0x00, 0x1 };
+    InputMemoryStream stream({ buf, sizeof(buf) });
+
+    // Only test with first byte expecting more, otherwise equivalent to single byte case
+    for (u16 i = 0x80; i <= 0xFF; ++i) {
+        buf[0] = static_cast<u8>(i);
+
+        // less than/eq 0b0011_1111: signed == unsigned == (j << 7) + (7 MSB of i)
+        for (u8 j = 0u; j <= 0x3F; ++j) {
+            buf[1] = j;
+
+            stream.seek(0);
+            EXPECT(LEB128::read_unsigned(stream, output));
+            EXPECT_EQ(output, (static_cast<u32>(j) << 7) + (i & 0x7F));
+            EXPECT(!stream.handle_any_error());
+
+            stream.seek(0);
+            EXPECT(LEB128::read_signed(stream, output_signed));
+            EXPECT_EQ(output_signed, (static_cast<i32>(j) << 7) + (i & 0x7F));
+            EXPECT(!stream.handle_any_error());
+        }
+
+        // 0b0100_0000 to 0b0111_1111: unsigned == (j << 7) + (7 MSB of i), signed == {{ 19'b(-1), 6'b(j), 7'b(i) }}
+        for (u8 j = 0x40u; j < 0x80; ++j) {
+            buf[1] = j;
+
+            stream.seek(0);
+            EXPECT(LEB128::read_unsigned(stream, output));
+            EXPECT_EQ(output, (static_cast<u32>(j) << 7) + (i & 0x7F));
+            EXPECT(!stream.handle_any_error());
+
+            stream.seek(0);
+            EXPECT(LEB128::read_signed(stream, output_signed));
+            EXPECT_EQ(output_signed, ((static_cast<i32>(j) << 7) + (i & 0x7F)) | (-1 & (~0x3FFF)));
+            EXPECT(!stream.handle_any_error());
+        }
+
+        // MSB set on last byte, but input too short
+        for (u16 j = 0x80; j <= 0xFF; ++j) {
+            buf[1] = static_cast<u8>(j);
+
+            stream.seek(0);
+            EXPECT(!LEB128::read_unsigned(stream, output));
+            EXPECT(stream.handle_any_error());
+
+            stream.seek(0);
+            EXPECT(!LEB128::read_signed(stream, output_signed));
+            EXPECT(stream.handle_any_error());
+        }
+    }
+}