diff --git a/compiler/testData/diagnostics/ReadMe.md b/compiler/testData/diagnostics/ReadMe.md
index 014110bb098..78ed94e36c9 100644
--- a/compiler/testData/diagnostics/ReadMe.md
+++ b/compiler/testData/diagnostics/ReadMe.md
@@ -41,4 +41,15 @@ With that, an exact type of an expression can be checked in the following way:
 
 #### Usage:
 
-    // !CHECK_TYPE
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+    // !CHECK_TYPE
+
+### 3. FILE
+
+The directive let you compose a test consisting of several files in one actual file.
+
+#### Usage:
+// FILE: A.java
+/* Java code */
+
+// FILE: B.kt
+/* kotlin code */
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