DATACMNS-1304 - Polishing.

Moved test cases into PropertyPathUnit test so that they're closer to the implementation. Switched to Introspector.decapitalize(…) to follow the Java Beans Specification regarding the handling of all-uppercase properties.

Original pull request: #289.

src/test/java/org/springframework/data/mapping/PropertyPathUnitTests.java

@@ -386,6 +386,21 @@ public class PropertyPathUnitTests {
 				.isThrownBy(() -> PropertyPath.from(path, Left.class));
 	}
 
+	@Test // DATACMNS-1304
+	public void resolvesPropertyPathWithSingleUppercaseLetterPropertyEnding() {
+		assertThat(from("categoryB", Product.class).toDotPath()).isEqualTo("categoryB");
+	}
+
+	@Test // DATACMNS-1304
+	public void resolvesPropertyPathWithUppercaseLettersPropertyEnding() {
+		assertThat(from("categoryABId", Product.class).toDotPath()).isEqualTo("categoryAB.id");
+	}
+
+	@Test // DATACMNS-1304
+	public void detectsNestedSingleCharacterProperty() {
+		assertThat(from("category_B", Product.class).toDotPath()).isEqualTo("category.b");
+	}
+
 	private class Foo {
 
 		String userName;
@@ -430,4 +445,18 @@ public class PropertyPathUnitTests {
 	private class Right {
 		Left bar;
 	}
+
+	// DATACMNS-1304
+	private class Product {
+		Category category;
+		Category categoryB;
+		Category categoryAB;
+	}
+
+	private class Category {
+		B b;
+		String id;
+	}
+
+	private class B {}
 }