Add and fix tests for overridden bindings

The order of property values is only preserved if we check carefully
that each property is actually present in the source being inspected.

Fixes gh-3385

spring-boot/src/main/java/org/springframework/boot/bind/PropertySourcesPropertyValues.java

@@ -153,6 +153,9 @@ public class PropertySourcesPropertyValues implements PropertyValues {
 			PropertySourcesPropertyResolver resolver,
 			PropertyNamePatternsMatcher includes, Collection<String> exacts) {
 		for (String propertyName : exacts) {
+			if (!source.containsProperty(propertyName)) {
+				continue;
+			}
 			Object value = null;
 			try {
 				value = resolver.getProperty(propertyName, Object.class);

spring-boot/src/test/java/org/springframework/boot/bind/PropertySourcesBindingTests.java

@@ -57,6 +57,16 @@ public class PropertySourcesBindingTests {
 		assertThat(this.properties.getBar(), is("override"));
 	}
 
+	@Test
+	public void overridingOfPropertiesOrderOfAtPropertySourcesWherePropertyIsCapitalized() {
+		assertThat(this.properties.getSpam(), is("BUCKET"));
+	}
+
+	@Test
+	public void overridingOfPropertiesOrderOfAtPropertySourcesWherePropertyNamesDiffer() {
+		assertThat(this.properties.getTheName(), is("NAME"));
+	}
+
 	@Test
 	public void overridingOfPropertiesAndBindToAtValue() {
 		assertThat(this.foo, is(this.properties.getFoo()));
@@ -93,6 +103,10 @@ public class PropertySourcesBindingTests {
 
 		private String bar;
 
+		private String spam;
+
+		private String theName;
+
 		public String getBar() {
 			return this.bar;
 		}
@@ -108,6 +122,22 @@ public class PropertySourcesBindingTests {
 		public void setFoo(String foo) {
 			this.foo = foo;
 		}
+
+		public String getSpam() {
+			return this.spam;
+		}
+
+		public void setSpam(String spam) {
+			this.spam = spam;
+		}
+
+		public String getTheName() {
+			return this.theName;
+		}
+
+		public void setTheName(String theName) {
+			this.theName = theName;
+		}
 	}
 
 }

spring-boot/src/test/resources/override.properties

 foo=bar
 bar=override
+SPAM=BUCKET
+THE_NAME=NAME
\ No newline at end of file

spring-boot/src/test/resources/some.properties

 foo=spam
-bar=some
+bar=some
\ No newline at end of file
+spam=bucket
+the-name=name
\ No newline at end of file