diff --git a/extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeDescriptionHelperTest.java b/extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeDescriptionHelperTest.java
new file mode 100644
index 000000000..7c0713651
--- /dev/null
+++ b/extractor/src/test/java/org/schabi/newpipe/extractor/services/youtube/YoutubeDescriptionHelperTest.java
@@ -0,0 +1,81 @@
+package org.schabi.newpipe.extractor.services.youtube;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.schabi.newpipe.extractor.services.youtube.YoutubeDescriptionHelper.runsToHtml;
+
+import org.junit.jupiter.api.Test;
+import org.schabi.newpipe.extractor.services.youtube.YoutubeDescriptionHelper.Run;
+
+import java.util.Comparator;
+import java.util.List;
+import java.util.function.Function;
+import java.util.stream.Collectors;
+
+public class YoutubeDescriptionHelperTest {
+
+    private static void assertRunsToHtml(final String expectedHtml,
+                                         final List<Run> openers,
+                                         final List<Run> closers,
+                                         final String content) {
+        assertEquals(
+                expectedHtml,
+                runsToHtml(
+                        openers.stream()
+                                .sorted(Comparator.comparingInt(run -> run.pos))
+                                .collect(Collectors.toList()),
+                        closers.stream()
+                                .sorted(Comparator.comparingInt(run -> run.pos))
+                                .collect(Collectors.toList()),
+                        content
+                )
+        );
+    }
+
+    @Test
+    public void testNoRuns() {
+        assertRunsToHtml(
+                "abc *a* _c_ <br> <br> <a href=\"#\">test</a> &nbsp;&amp;",
+                List.of(),
+                List.of(),
+                "abc *a* _c_ <br>\u00a0\n\u00a0<a href=\"#\">test</a>  &amp;"
+        );
+    }
+
+    @Test
+    public void testNormalRuns() {
+        assertRunsToHtml(
+                "<A>hel<B>lo </B>nic</A>e <C>test</C>",
+                List.of(new Run("<A>", "</A>", 0), new Run("<B>", "</B>", 3),
+                        new Run("<C>", "</C>", 11)),
+                List.of(new Run("<A>", "</A>", 9), new Run("<B>", "</B>", 6),
+                        new Run("<C>", "</C>", 15)),
+                "hello nice test"
+        );
+    }
+
+    @Test
+    public void testOverlappingRuns() {
+        assertRunsToHtml(
+                "01<A>23<B>45</B></A><B>67</B>89",
+                List.of(new Run("<A>", "</A>", 2), new Run("<B>", "</B>", 4)),
+                List.of(new Run("<A>", "</A>", 6), new Run("<B>", "</B>", 8)),
+                "0123456789"
+        );
+    }
+
+    @Test
+    public void testTransformingRuns() {
+        final Function<String, String> tA = content -> "whatever";
+        final Function<String, String> tD
+                = content -> Integer.parseInt(content) % 2 == 0 ? "even" : "odd";
+
+        assertRunsToHtml(
+                "0<A>whatever</A><C>4</C>5<D>odd</D>89",
+                List.of(new Run("<A>", "</A>", 1, tA), new Run("<B>", "</B>", 2),
+                        new Run("<C>", "</C>", 3), new Run("<D>", "</D>", 6, tD)),
+                List.of(new Run("<A>", "</A>", 4, tA), new Run("<B>", "</B>", 3),
+                        new Run("<C>", "</C>", 5), new Run("<D>", "</D>", 8, tD)),
+                "0123456789"
+        );
+    }
+}