[issue #1377] [test-case] Added test that proves @Singular is not removed

test/transform/resource/before/SingularCleanupForDelombok.java

@@ -0,0 +1,23 @@
+// issue #1377: @Singular is not removed by delombok.
+
+import java.util.Set;
+
+import lombok.AccessLevel;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Getter;
+import lombok.NonNull;
+import lombok.Singular;
+
+import lombok.experimental.Accessors;
+import lombok.experimental.FieldDefaults;
+
+@Accessors(fluent = true) @AllArgsConstructor(access = AccessLevel.PACKAGE) @FieldDefaults(makeFinal = true, level = AccessLevel.PRIVATE) class Book {
+	@Getter @NonNull String name;
+	@Getter @Singular @NonNull Set<String> authors;
+	int numberOfAuthors;
+	
+	@Builder public Book(String name, @Singular Set<String> authors) {
+		this(name, authors, authors.size());
+	}
+}