diff --git a/src/main/java/net/kemitix/wiser/assertions/WiserAssertions.java b/src/main/java/net/kemitix/wiser/assertions/WiserAssertions.java
index 5d93ae9..50dbf4c 100644
--- a/src/main/java/net/kemitix/wiser/assertions/WiserAssertions.java
+++ b/src/main/java/net/kemitix/wiser/assertions/WiserAssertions.java
@@ -1,5 +1,8 @@
 package net.kemitix.wiser.assertions;
 
+import org.subethamail.wiser.Wiser;
+import org.subethamail.wiser.WiserMessage;
+
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
@@ -7,55 +10,137 @@ import java.text.MessageFormat;
 import java.util.List;
 import java.util.function.Predicate;
 import java.util.function.Supplier;
+
 import javax.mail.MessagingException;
 import javax.mail.internet.MimeMessage;
 import javax.mail.internet.MimeMultipart;
-import org.subethamail.wiser.Wiser;
-import org.subethamail.wiser.WiserMessage;
 
 /**
- * Taken from the WiserAssetions class from Rafal Browiec at
- * http://blog.codeleak.pl/2014/09/testing-mail-code-in-spring-boot.html
+ * Provides a set of assertions for checking the status of any messages received
+ * by subethamail's Wiser.
+ *
+ * <pre>
+ * {@code
+ * {@literal @}Before
+ * public void setUp() throws IOException {
+ *     wiser = new Wiser(PORT);
+ *     wiser.start();
+ * }
+ *
+ * {@literal @}After public void tearDown() { wiser.stop(); }
+ *
+ * {@literal @}Test public void testMail() { //given ...
+ *
+ * //when ...
+ *
+ * //then WiserAssertions.assertReceivedMessage(wiser) .from(sender)
+ * .to(recipient_alpha) .to(recipient_beta) .withSubjectContains(subject_prefix)
+ * .withSubjectContains(subject_suffix) .withContentContains(message_element_1)
+ * .withContentContains(message_element_2)
+ * .withContentContains(message_element_3); }
+ * }
+ * </pre>
  */
-public class WiserAssertions {
+public final class WiserAssertions {
 
+    /**
+     * The messages received by Wiser.
+     */
     private final List<WiserMessage> messages;
 
-    public static WiserAssertions assertReceivedMessage(Wiser wiser) {
+    /**
+     * Creates an instance of {@code} WiserAssertions} ready to make assertions
+     * on any messages received by the {@link Wiser} server.
+     *
+     * @param wiser the SMTP server instance
+     *
+     * @return an instance of {@code WiserAssertions}
+     */
+    public static WiserAssertions assertReceivedMessage(final Wiser wiser) {
         return new WiserAssertions(wiser.getMessages());
     }
 
-    private WiserAssertions(List<WiserMessage> messages) {
-        this.messages = messages;
+    /**
+     * Private constructor.
+     *
+     * @param wiserMessages the messages to be tested by the assertions
+     */
+    private WiserAssertions(final List<WiserMessage> wiserMessages) {
+        this.messages = wiserMessages;
     }
 
-    public WiserAssertions from(String from) {
-        findFirstOrElseThrow(m -> m.getEnvelopeSender().equals(from),
-                assertionError("No message from [{0}] found!", from));
+    /**
+     * Checks that there was at least one email received that was sent from the
+     * {@code sender}.
+     *
+     * @param sender email address to search for
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions from(final String sender) {
+        findFirstOrElseThrow(m -> m.getEnvelopeSender().equals(sender),
+                assertionError("No message from [{0}] found!", sender));
         return this;
     }
 
-    public WiserAssertions to(String to) {
-        findFirstOrElseThrow(m -> m.getEnvelopeReceiver().equals(to),
-                assertionError("No message to [{0}] found!", to));
+    /**
+     * Checks that there was at least one email received that was sent to the
+     * {@code recipient}.
+     *
+     * @param recipient email address to search for
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions to(final String recipient) {
+        findFirstOrElseThrow(m -> m.getEnvelopeReceiver().equals(recipient),
+                assertionError("No message to [{0}] found!", recipient));
         return this;
     }
 
-    public WiserAssertions withSubject(String subject) {
-        Predicate<WiserMessage> predicate = m -> subject.equals(unchecked(getMimeMessage(m)::getSubject));
+    /**
+     * Checks that there was at least one email received that has the required
+     * subject.
+     *
+     * @param subject the subject line to search for
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions withSubject(final String subject) {
+        Predicate<WiserMessage> predicate
+                = m -> subject.equals(unchecked(getMimeMessage(m)::getSubject));
         findFirstOrElseThrow(predicate,
-                assertionError("No message with subject [{0}] found!", subject));
+                assertionError("No message with subject [{0}] found!",
+                        subject));
         return this;
     }
 
-    public WiserAssertions withSubjectContains(String subject) {
-        Predicate<WiserMessage> predicate = m -> unchecked(getMimeMessage(m)::getSubject).contains(subject);
+    /**
+     * Checks that there was at least one email received that has a subject that
+     * contains the search text.
+     *
+     * @param subject the text to search for in the subject
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions withSubjectContains(final String subject) {
+        Predicate<WiserMessage> predicate
+                = m -> unchecked(getMimeMessage(m)::getSubject)
+                .contains(subject);
         findFirstOrElseThrow(predicate,
-                assertionError("No message with subject [{0}] found!", subject));
+                assertionError("No message with subject [{0}] found!",
+                        subject));
         return this;
     }
 
-    public WiserAssertions withContent(String content) {
+    /**
+     * Check that there was at least one email received that has a body that
+     * matches the content.
+     *
+     * @param content the body of the email to search for
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions withContent(final String content) {
         findFirstOrElseThrow(m -> {
             ThrowingSupplier<String> contentAsString
                     = () -> getMimeMessageBody(m).trim();
@@ -64,19 +149,40 @@ public class WiserAssertions {
         return this;
     }
 
-    public WiserAssertions withContentContains(String content) {
+    /**
+     * Check that there was at least one email received that contains the search
+     * text.
+     *
+     * @param content the text to search for in the body of the email
+     *
+     * @return the {@code WiserAssertions} instance
+     */
+    public WiserAssertions withContentContains(final String content) {
         StringBuilder messageContent = new StringBuilder();
         findFirstOrElseThrow((WiserMessage m) -> {
             ThrowingSupplier<String> contentAsString
                     = () -> getMimeMessageBody(m).trim();
             messageContent.append(unchecked(contentAsString));
             return unchecked(contentAsString).contains(content);
-        }, assertionError("No message with content containing [{0}] found! Was {1}", content, messageContent));
+        }, assertionError(
+                "No message with content containing [{0}] found! Was {1}",
+                content, messageContent));
         return this;
     }
 
-    private String getMimeMessageBody(WiserMessage m) throws IOException, MessagingException {
-        Object content = getMimeMessage(m).getContent();
+    /**
+     * Returns the body of the message.
+     *
+     * @param message the message
+     *
+     * @return the body of the message
+     *
+     * @throws IOException        if error extracting the mime message
+     * @throws MessagingException if the message type is not known
+     */
+    private String getMimeMessageBody(final WiserMessage message)
+            throws IOException, MessagingException {
+        Object content = getMimeMessage(message).getContent();
         if (content instanceof MimeMessage) {
             return (String) content;
         }
@@ -86,20 +192,63 @@ public class WiserAssertions {
         throw new RuntimeException("Unexpected MimeMessage content");
     }
 
-    private void findFirstOrElseThrow(Predicate<WiserMessage> predicate, Supplier<AssertionError> exceptionSupplier) {
+    /**
+     * Checks that at least on message matches the predicate or the supplied
+     * exception will be thrown.
+     *
+     * @param predicate         the condition a message must match
+     * @param exceptionSupplier the supplier of the exception
+     */
+    private void findFirstOrElseThrow(
+            final Predicate<WiserMessage> predicate,
+            final Supplier<AssertionError> exceptionSupplier
+    ) {
         messages.stream().filter(predicate)
                 .findFirst().orElseThrow(exceptionSupplier);
     }
 
-    private MimeMessage getMimeMessage(WiserMessage wiserMessage) {
+    /**
+     * Returns the mime message within the {@link WiserMessage} converting any
+     * {@link MessagingException}s into {@link RuntimeException}s.
+     *
+     * @param wiserMessage the message
+     *
+     * @return the mime message
+     */
+    private MimeMessage getMimeMessage(final WiserMessage wiserMessage) {
         return unchecked(wiserMessage::getMimeMessage);
     }
 
-    private static Supplier<AssertionError> assertionError(String errorMessage, Object... args) {
-        return () -> new AssertionError(MessageFormat.format(errorMessage, args));
+    /**
+     * Returns a {@link Supplier} for an {@link AssertionError}.
+     *
+     * @param errorMessage the message for the exception
+     * @param args         the parameters to insert into the message using
+     *                     {@link MessageFormat}
+     *
+     * @return a supplier of an {@link AssertionError}
+     */
+    @SuppressWarnings(
+            {"ThrowableInstanceNotThrown", "ThrowableInstanceNeverThrown"})
+    private static Supplier<AssertionError> assertionError(
+            final String errorMessage,
+            final Object... args
+    ) {
+        return ()
+                -> new AssertionError(MessageFormat.format(errorMessage, args));
     }
 
-    public static <T> T unchecked(ThrowingSupplier<T> supplier) {
+    /**
+     * Convert any checked Exceptions into unchecked Exceptions.
+     *
+     * @param <T>      the item type to be returned after suppressing any
+     *                 checked exceptions
+     * @param supplier the source of the return value that could cause a checked
+     *                 exception
+     *
+     * @return the product of the supplier
+     */
+    public static <T> T unchecked(final ThrowingSupplier<T> supplier) {
         try {
             return supplier.get();
         } catch (Throwable e) {
@@ -107,14 +256,38 @@ public class WiserAssertions {
         }
     }
 
-    private String getMimeMultipartAsString(MimeMultipart mimeMultipart) throws MessagingException, IOException {
+    /**
+     * Converts a {@link MimeMultipart} into a {@link String}.
+     *
+     * @param mimeMultipart the message part to convert
+     *
+     * @return the message part as a string
+     *
+     * @throws MessagingException if the part is empty
+     * @throws IOException        if there is another error
+     */
+    private String getMimeMultipartAsString(final MimeMultipart mimeMultipart)
+            throws MessagingException, IOException {
         OutputStream os = new ByteArrayOutputStream();
         mimeMultipart.writeTo(os);
         return os.toString();
     }
 
+    /**
+     * Interface for providing a value that could thrown an exception when
+     * sought.
+     *
+     * @param <T> the type of value to be supplied
+     */
     public interface ThrowingSupplier<T> {
 
+        /**
+         * Returns the value.
+         *
+         * @return the value
+         *
+         * @throws Throwable on error
+         */
         T get() throws Throwable;
     }
 }