Introduce ApprovalTests (https://approvaltests.com/)

- It opens a diff window when comparing Strings and File contents

pom.xml

@@ -34,6 +34,7 @@
         <assertj.version>3.21.0</assertj.version>
         <spotless.version>2.12.2</spotless.version>
         <google-java-format.version>1.7</google-java-format.version>
+        <approvaltests.version>24.2.0</approvaltests.version>
     </properties>
 
     <dependencies>
@@ -49,6 +50,12 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>com.approvaltests</groupId>
+            <artifactId>approvaltests</artifactId>
+            <version>${approvaltests.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>
@@ -66,6 +73,9 @@
                                 <include>.gitignore</include>
                                 <include>.gitattributes</include>
                             </includes>
+                            <excludes>
+                                <exclude>src/test/approvals/**</exclude>
+                            </excludes>
                             <trimTrailingWhitespace />
                             <endWithNewline />
                             <indent>

src/test/approvals/org/codejive/properties/TestProperties.testStoreOutputStream.approved.txt

@@ -0,0 +1,17 @@
+#comment1
+#  comment2
+
+! comment3
+one=simple
+two=value containing spaces
+# another comment
+! and a comment
+! block
+three=and escapes\n\t\r\f
+\ with\ spaces   =    everywhere  
+altsep:value
+multiline = one \
+    two  \
+	three
+key.4 = \u1234\u1234
+# final comment

src/test/java/org/codejive/properties/PackageSettings.java

@@ -0,0 +1,12 @@
+package org.codejive.properties;
+
+/**
+ * This class is used by the ApprovalTests framework
+ *
+ * @see <a
+ *     href="https://github.com/approvals/ApprovalTests.Java/blob/master/approvaltests/docs/Configuration.md#package-level-settings">ApprovalTests
+ *     Configuration</a>
+ */
+public class PackageSettings {
+    public static String ApprovalBaseDirectory = "../approvals";
+}

src/test/java/org/codejive/properties/TestProperties.java

@@ -11,6 +11,7 @@
 import java.util.Collections;
 import java.util.Iterator;
 import java.util.NoSuchElementException;
+import org.approvaltests.Approvals;
 import org.junit.jupiter.api.Test;
 
 public class TestProperties {
@@ -124,7 +125,7 @@ void testStoreOutputStream() throws IOException, URISyntaxException {
         Properties p = Properties.loadProperties(f);
         ByteArrayOutputStream os = new ByteArrayOutputStream();
         p.store(os);
-        assertThat(os.toString()).isEqualTo(readAll(f));
+        Approvals.verify(os.toString());
     }
 
     @Test