Add additional AssertJ examples

.gitignore

@@ -27,3 +27,4 @@ target/
 
 spring-openid/src/main/resources/application.properties
 .recommenders/
+

assertj/src/test/java/com/baeldung/assertj/introduction/AssertJCoreTest.java

@@ -2,17 +2,23 @@ package com.baeldung.assertj.introduction;
 
 import com.baeldung.assertj.introduction.domain.Dog;
 import com.baeldung.assertj.introduction.domain.Person;
+import org.assertj.core.util.Maps;
 import org.junit.Ignore;
 import org.junit.Test;
 
+import java.io.ByteArrayInputStream;
+import java.io.File;
+import java.io.InputStream;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
 import java.util.NoSuchElementException;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.entry;
 import static org.assertj.core.api.Assertions.withPrecision;
 
-public class AssertJDemoTest {
+public class AssertJCoreTest {
 
     @Test
     public void whenComparingReferences_thenNotEqual() throws Exception {
@@ -42,6 +48,10 @@ public class AssertJDemoTest {
     public void whenCheckingForElement_thenMultipleAssertions() throws Exception {
         List<String> list = Arrays.asList("1", "2", "3");
 
+        assertThat(list).isNotEmpty();
+        assertThat(list).startsWith("1");
+        assertThat(list).doesNotContainNull();
+
         assertThat(list)
                 .isNotEmpty()
                 .contains("1")
@@ -55,6 +65,17 @@ public class AssertJDemoTest {
         assertThat(Runnable.class).isInterface();
     }
 
+    @Test
+    public void whenCheckingCharacter_thenIsUnicode() throws Exception {
+        char someCharacter = 'c';
+
+        assertThat(someCharacter)
+                .isNotEqualTo('a')
+                .inUnicode()
+                .isGreaterThanOrEqualTo('b')
+                .isLowerCase();
+    }
+
     @Test
     public void whenAssigningNSEExToException_thenIsAssignable() throws Exception {
         assertThat(Exception.class).isAssignableFrom(NoSuchElementException.class);
@@ -65,6 +86,51 @@ public class AssertJDemoTest {
         assertThat(5.1).isEqualTo(5, withPrecision(1d));
     }
 
+    @Test
+    public void whenCheckingString_then() throws Exception {
+        assertThat("".isEmpty()).isTrue();
+    }
+
+    @Test
+    public void whenCheckingFile_then() throws Exception {
+        final File someFile = File.createTempFile("aaa", "bbb");
+        someFile.deleteOnExit();
+
+        assertThat(someFile)
+                .exists()
+                .isFile()
+                .canRead()
+                .canWrite();
+    }
+
+    @Test
+    public void whenCheckingIS_then() throws Exception {
+        InputStream given = new ByteArrayInputStream("foo".getBytes());
+        InputStream expected = new ByteArrayInputStream("foo".getBytes());
+
+        assertThat(given).hasSameContentAs(expected);
+    }
+
+    @Test
+    public void whenGivenMap_then() throws Exception {
+        Map<Integer, String> map = Maps.newHashMap(2, "a");
+
+        assertThat(map)
+                .isNotEmpty()
+                .containsKey(2)
+                .doesNotContainKeys(10)
+                .contains(entry(2, "a"));
+    }
+
+    @Test
+    public void whenGivenException_then() throws Exception {
+        Exception ex = new Exception("abc");
+
+        assertThat(ex)
+                .hasNoCause()
+                .hasMessageEndingWith("c");
+    }
+
     @Ignore // IN ORDER TO TEST, REMOVE THIS LINE
     @Test
     public void whenRunningAssertion_thenDescribed() throws Exception {