diff --git a/platform/projectModel-api/src/com/intellij/openapi/roots/FileIndex.java b/platform/projectModel-api/src/com/intellij/openapi/roots/FileIndex.java
index 64558ddc5889..99eec952f1d9 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/roots/FileIndex.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/roots/FileIndex.java
@@ -57,6 +57,7 @@ public interface FileIndex {
 
   /**
    * Returns true if <code>file</code> is a source file which belongs to sources of the content.
+   * (Returns true for both source and test source).<p/>
    * Note that sometimes a file can belong to the content and be a source file but not belong to sources of the content.
    * This happens if sources of some library are located under the content (so they belong to the project content but not as sources).
    *
diff --git a/platform/projectModel-api/src/com/intellij/openapi/roots/ProjectFileIndex.java b/platform/projectModel-api/src/com/intellij/openapi/roots/ProjectFileIndex.java
index fdae3317e74e..d47f640926d5 100644
--- a/platform/projectModel-api/src/com/intellij/openapi/roots/ProjectFileIndex.java
+++ b/platform/projectModel-api/src/com/intellij/openapi/roots/ProjectFileIndex.java
@@ -125,7 +125,7 @@ public interface ProjectFileIndex extends FileIndex {
   boolean isLibraryClassFile(@NotNull VirtualFile file);
 
   /**
-   * Returns true if <code>fileOrDir</code> is a file or directory from the content source or library sources.
+   * Returns true if <code>fileOrDir</code> is a file or directory from the content production/test source or library source.
    *
    * @param fileOrDir the file or directory to check.
    * @return true if the file or directory belongs to project or library sources, false otherwise.