diff --git a/.idea/jarRepositories.xml b/.idea/jarRepositories.xml
index 710766b..0e29f96 100644
--- a/.idea/jarRepositories.xml
+++ b/.idea/jarRepositories.xml
@@ -16,6 +16,11 @@
       <option name="name" value="MavenLocal" />
       <option name="url" value="file:$MAVEN_REPOSITORY$/" />
     </remote-repository>
+    <remote-repository>
+      <option name="id" value="MavenLocal" />
+      <option name="name" value="MavenLocal" />
+      <option name="url" value="file:$MAVEN_REPOSITORY$/" />
+    </remote-repository>
     <remote-repository>
       <option name="id" value="maven2" />
       <option name="name" value="maven2" />
diff --git a/.idea/misc.xml b/.idea/misc.xml
index fec46c9..c55072b 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -1,5 +1,8 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="ExternalStorageConfigurationManager" enabled="true" />
+  <component name="FrameworkDetectionExcludesConfiguration">
+    <file type="web" url="file://$PROJECT_DIR$" />
+  </component>
   <component name="ProjectRootManager" version="2" languageLevel="JDK_11" project-jdk-name="18" project-jdk-type="JavaSDK" />
 </project>
\ No newline at end of file
diff --git a/config/detekt/baseline.xml b/config/detekt/baseline.xml
index 1435fa5..c9c57d9 100644
--- a/config/detekt/baseline.xml
+++ b/config/detekt/baseline.xml
@@ -52,11 +52,13 @@
     <ID>NestedBlockDepth:LinksMgr.kt$LinksMgr$override fun commandResponse(channel: String, args: String, event: GenericMessageEvent)</ID>
     <ID>NestedBlockDepth:Lookup.kt$Lookup$override fun commandResponse(channel: String, cmd: String, args: String, event: GenericMessageEvent)</ID>
     <ID>NestedBlockDepth:Posting.kt$Posting$override fun commandResponse(channel: String, args: String, event: GenericMessageEvent)</ID>
+    <ID>NestedBlockDepth:Seen.kt$Seen$fun add(nick: String)</ID>
+    <ID>NestedBlockDepth:Seen.kt$Seen$override fun commandResponse(channel: String, args: String, event: GenericMessageEvent)</ID>
     <ID>NestedBlockDepth:StockQuote.kt$StockQuote.Companion$@JvmStatic @Throws(ModuleException::class) fun getQuote(symbol: String, apiKey: String?): List&lt;Message&gt;</ID>
     <ID>NestedBlockDepth:Tell.kt$Tell$fun send(event: GenericUserEvent)</ID>
-    <ID>NestedBlockDepth:TellMessagesMgr.kt$TellMessagesMgr$@JvmStatic fun load(file: String): List&lt;TellMessage&gt;</ID>
-    <ID>NestedBlockDepth:TellMessagesMgr.kt$TellMessagesMgr$@JvmStatic fun save(file: String, messages: List&lt;TellMessage?&gt;?)</ID>
     <ID>NestedBlockDepth:TwitterOAuth.kt$TwitterOAuth$@JvmStatic @Throws(TwitterException::class, IOException::class) fun main(args: Array&lt;String&gt;)</ID>
+    <ID>NestedBlockDepth:Utils.kt$Utils$@JvmStatic fun loadData(file: String, default: Any, logger: Logger, description: String): Any</ID>
+    <ID>NestedBlockDepth:Utils.kt$Utils$@JvmStatic fun saveData(file: String, data: Any, logger: Logger, description: String)</ID>
     <ID>NestedBlockDepth:Weather2.kt$Weather2$override fun run(channel: String, cmd: String, args: String, event: GenericMessageEvent)</ID>
     <ID>NestedBlockDepth:Weather2.kt$Weather2.Companion$@JvmStatic @Throws(ModuleException::class) fun getWeather(query: String, apiKey: String?): List&lt;Message&gt;</ID>
     <ID>ReturnCount:Addons.kt$Addons$fun exec(channel: String, cmd: String, args: String, event: GenericMessageEvent): Boolean</ID>
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/Mobibot.kt b/src/main/kotlin/net/thauvin/erik/mobibot/Mobibot.kt
index 2e686af..6cbefa9 100644
--- a/src/main/kotlin/net/thauvin/erik/mobibot/Mobibot.kt
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/Mobibot.kt
@@ -65,6 +65,7 @@ import net.thauvin.erik.mobibot.commands.links.LinksMgr
 import net.thauvin.erik.mobibot.commands.links.Posting
 import net.thauvin.erik.mobibot.commands.links.Tags
 import net.thauvin.erik.mobibot.commands.links.View
+import net.thauvin.erik.mobibot.commands.seen.Seen
 import net.thauvin.erik.mobibot.commands.tell.Tell
 import net.thauvin.erik.mobibot.modules.Calc
 import net.thauvin.erik.mobibot.modules.CryptoPrices
@@ -113,7 +114,10 @@ class Mobibot(nickname: String, val channel: String, logsDirPath: String, p: Pro
     // Commands and Modules
     private val addons: Addons
 
-    // Tell module
+    // Seen command
+    private val seen: Seen
+
+    // Tell command
     private val tell: Tell
 
     /** Logger. */
@@ -231,6 +235,8 @@ class Mobibot(nickname: String, val channel: String, logsDirPath: String, p: Pro
             with(event.getBot<PircBotX>()) {
                 if (user.nick == nick) {
                     LinksMgr.twitter.notification("$nick has left ${event.channel.name} on irc://$serverHostname")
+                } else {
+                    seen.add(user.nick)
                 }
             }
         }
@@ -253,7 +259,7 @@ class Mobibot(nickname: String, val channel: String, logsDirPath: String, p: Pro
                 Constants.PROPS_ARG,
                 Constants.PROPS_ARG.substring(0, 1),
                 "Use alternate properties file"
-            ).default("./mobibot.properties")
+            ).default("./${ReleaseInfo.PROJECT}.properties")
             val version by parser.option(
                 ArgType.Boolean,
                 Constants.VERSION_ARG,
@@ -355,6 +361,7 @@ class Mobibot(nickname: String, val channel: String, logsDirPath: String, p: Pro
                 nickservCustomMessage = identMsg
             }
             isAutoReconnect = true
+
             //socketConnectTimeout = Constants.CONNECT_TIMEOUT
             //socketTimeout = Constants.CONNECT_TIMEOUT
             //messageDelay = StaticDelay(500)
@@ -388,6 +395,11 @@ class Mobibot(nickname: String, val channel: String, logsDirPath: String, p: Pro
         addons.add(Posting())
         addons.add(Recap())
         addons.add(Say())
+
+        // Seen command
+        seen = Seen("${logsDirPath}${nickname}-seen.ser")
+        addons.add(seen)
+
         addons.add(Tags())
 
         // Tell command
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/Utils.kt b/src/main/kotlin/net/thauvin/erik/mobibot/Utils.kt
index 69bb38b..0812339 100644
--- a/src/main/kotlin/net/thauvin/erik/mobibot/Utils.kt
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/Utils.kt
@@ -38,18 +38,27 @@ import org.pircbotx.Colors
 import org.pircbotx.PircBotX
 import org.pircbotx.hooks.events.PrivateMessageEvent
 import org.pircbotx.hooks.types.GenericMessageEvent
+import org.slf4j.Logger
+import java.io.BufferedInputStream
+import java.io.BufferedOutputStream
 import java.io.BufferedReader
 import java.io.IOException
 import java.io.InputStreamReader
+import java.io.ObjectInputStream
+import java.io.ObjectOutputStream
 import java.net.URL
 import java.net.URLEncoder
 import java.nio.charset.StandardCharsets
+import java.nio.file.Files
+import java.nio.file.Paths
 import java.time.LocalDateTime
 import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 import java.util.Date
 import java.util.Properties
 import java.util.stream.Collectors
+import kotlin.io.path.exists
+import kotlin.io.path.fileSize
 
 /**
  * Miscellaneous utilities.
@@ -188,6 +197,29 @@ object Utils {
             ""
     }
 
+    /**
+     * Load data.
+     */
+    @JvmStatic
+    fun loadData(file: String, default: Any, logger: Logger, description: String): Any {
+        val serialFile = Paths.get(file)
+        if (serialFile.exists() && serialFile.fileSize() > 0) {
+            try {
+                ObjectInputStream(
+                    BufferedInputStream(Files.newInputStream(serialFile))
+                ).use { input ->
+                    if (logger.isDebugEnabled) logger.debug("Loading the ${description}.")
+                    return input.readObject()
+                }
+            } catch (e: IOException) {
+                logger.error("An IO error occurred loading the ${description}.", e)
+            } catch (e: ClassNotFoundException) {
+                logger.error("An error occurred loading the {$description}.", e)
+            }
+        }
+        return default
+    }
+
     /**
      * Returns {@code true} if the list does not contain the given string.
      */
@@ -238,6 +270,23 @@ object Utils {
     @JvmStatic
     fun String?.reverseColor(): String = colorize(Colors.REVERSE)
 
+    /**
+     * Save data
+     */
+    @JvmStatic
+    fun saveData(file: String, data: Any, logger: Logger, description: String) {
+        try {
+            BufferedOutputStream(Files.newOutputStream(Paths.get(file))).use { bos ->
+                ObjectOutputStream(bos).use { output ->
+                    if (logger.isDebugEnabled) logger.debug("Saving the ${description}.")
+                    output.writeObject(data)
+                }
+            }
+        } catch (e: IOException) {
+            logger.error("Unable to save the ${description}.", e)
+        }
+    }
+
     /**
      * Send a formatted commands/modules, etc. list.
      */
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/commands/Info.kt b/src/main/kotlin/net/thauvin/erik/mobibot/commands/Info.kt
index d176448..a8d2dbf 100644
--- a/src/main/kotlin/net/thauvin/erik/mobibot/commands/Info.kt
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/commands/Info.kt
@@ -63,7 +63,7 @@ class Info(private val tell: Tell) : AbstractCommand() {
          */
         @JvmStatic
         fun Long.toUptime(): String {
-            this.toDuration(DurationUnit.MILLISECONDS).toComponents { wholeDays, hours, minutes, _, _ ->
+            this.toDuration(DurationUnit.MILLISECONDS).toComponents { wholeDays, hours, minutes, seconds, _ ->
                 val years = wholeDays / 365
                 var days = wholeDays % 365
                 val months = days / 30
@@ -88,7 +88,11 @@ class Info(private val tell: Tell) : AbstractCommand() {
                         append(hours).append(" hour".plural(hours.toLong())).append(' ')
                     }
 
-                    append(minutes).append(" minute".plural(minutes.toLong()))
+                    if (minutes > 0) {
+                        append(minutes).append(" minute".plural(minutes.toLong()))
+                    } else {
+                        append(seconds).append(" second".plural(seconds.toLong()))
+                    }
 
                     return toString()
                 }
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/Seen.kt b/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/Seen.kt
new file mode 100644
index 0000000..cb02cad
--- /dev/null
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/Seen.kt
@@ -0,0 +1,118 @@
+/*
+ * Seen.kt
+ *
+ * Copyright (c) 2004-2022, Erik C. Thauvin (erik@thauvin.net)
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ *   Neither the name of this project nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package net.thauvin.erik.mobibot.commands.seen
+
+import net.thauvin.erik.mobibot.Utils.bot
+import net.thauvin.erik.mobibot.Utils.helpFormat
+import net.thauvin.erik.mobibot.Utils.loadData
+import net.thauvin.erik.mobibot.Utils.saveData
+import net.thauvin.erik.mobibot.Utils.sendMessage
+import net.thauvin.erik.mobibot.commands.AbstractCommand
+import net.thauvin.erik.mobibot.commands.Info.Companion.toUptime
+import org.pircbotx.hooks.types.GenericMessageEvent
+import org.slf4j.Logger
+import org.slf4j.LoggerFactory
+
+class Seen(private val serialObject: String) : AbstractCommand() {
+    private val logger: Logger = LoggerFactory.getLogger(Seen::class.java)
+    val seenNicks: MutableList<SeenNick> = mutableListOf()
+
+    override val name = "seen"
+    override val help = listOf("To view when a nickname was last seen:", helpFormat("%c $name <nick>"))
+    override val isOpOnly = false
+    override val isPublic = true
+    override val isVisible = true
+
+    override fun commandResponse(channel: String, args: String, event: GenericMessageEvent) {
+        if (isEnabled()) {
+            if (args.isNotBlank() && !args.contains(' ')) {
+                val ch = event.bot().userChannelDao.getChannel(channel)
+                ch.users.forEach {
+                    if (args.equals(it.nick, true)) {
+                        event.sendMessage("${it.nick} is on ${channel}.")
+                        return
+                    }
+                }
+                seenNicks.forEach {
+                    if (it.nick.equals(args, true)) {
+                        val lastSeen = System.currentTimeMillis() - it.last
+                        event.sendMessage("${it.nick} was last seen on $channel ${lastSeen.toUptime()} ago.")
+                        return
+                    }
+                }
+                event.sendMessage("I haven't seen $args on $channel lately.")
+            } else {
+                helpResponse(channel, args, event)
+            }
+        }
+    }
+
+    fun add(nick: String) {
+        if (isEnabled()) {
+            seenNicks.forEach {
+                if (it.nick.equals(nick, true)) {
+                    if (it.nick != nick) it.nick = nick
+                    it.last = System.currentTimeMillis()
+                    save()
+                    return
+                }
+            }
+            seenNicks.add(SeenNick(nick))
+            save()
+        }
+    }
+
+    fun clear() {
+        seenNicks.clear()
+    }
+
+    fun load() {
+        if (isEnabled()) {
+            @Suppress("UNCHECKED_CAST")
+            seenNicks += loadData(
+                serialObject,
+                mutableListOf<SeenNick>(),
+                logger,
+                "seen nicknames"
+            ) as MutableList<SeenNick>
+        }
+    }
+
+    fun save() {
+        saveData(serialObject, seenNicks, logger, "seen nicknames")
+    }
+
+    init {
+        load()
+    }
+}
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenNick.kt b/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenNick.kt
new file mode 100644
index 0000000..0211dcc
--- /dev/null
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenNick.kt
@@ -0,0 +1,41 @@
+/*
+ * SeenNick.kt
+ *
+ * Copyright (c) 2004-2022, Erik C. Thauvin (erik@thauvin.net)
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ *   Neither the name of this project nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package net.thauvin.erik.mobibot.commands.seen
+
+import java.io.Serializable
+
+data class SeenNick(var nick: String, var last: Long = System.currentTimeMillis()) : Serializable {
+    companion object {
+        private const val serialVersionUID = 1L
+    }
+}
diff --git a/src/main/kotlin/net/thauvin/erik/mobibot/commands/tell/TellMessagesMgr.kt b/src/main/kotlin/net/thauvin/erik/mobibot/commands/tell/TellMessagesMgr.kt
index bb2f8cd..72897e6 100644
--- a/src/main/kotlin/net/thauvin/erik/mobibot/commands/tell/TellMessagesMgr.kt
+++ b/src/main/kotlin/net/thauvin/erik/mobibot/commands/tell/TellMessagesMgr.kt
@@ -31,18 +31,12 @@
  */
 package net.thauvin.erik.mobibot.commands.tell
 
+import net.thauvin.erik.mobibot.Utils.loadData
+import net.thauvin.erik.mobibot.Utils.saveData
 import org.slf4j.Logger
 import org.slf4j.LoggerFactory
-import java.io.BufferedInputStream
-import java.io.BufferedOutputStream
-import java.io.IOException
-import java.io.ObjectInputStream
-import java.io.ObjectOutputStream
-import java.nio.file.Files
-import java.nio.file.Paths
 import java.time.Clock
 import java.time.LocalDateTime
-import kotlin.io.path.exists
 
 /**
  * The Tell Messages Manager.
@@ -65,23 +59,8 @@ object TellMessagesMgr {
      */
     @JvmStatic
     fun load(file: String): List<TellMessage> {
-        val serialFile = Paths.get(file)
-        if (serialFile.exists()) {
-            try {
-                ObjectInputStream(
-                    BufferedInputStream(Files.newInputStream(serialFile))
-                ).use { input ->
-                    if (logger.isDebugEnabled) logger.debug("Loading the messages.")
-                    @Suppress("UNCHECKED_CAST")
-                    return input.readObject() as List<TellMessage>
-                }
-            } catch (e: IOException) {
-                logger.error("An IO error occurred loading the messages queue.", e)
-            } catch (e: ClassNotFoundException) {
-                logger.error("An error occurred loading the messages queue.", e)
-            }
-        }
-        return listOf()
+        @Suppress("UNCHECKED_CAST")
+        return loadData(file, emptyList<TellMessage>(), logger, "message queue") as List<TellMessage>
     }
 
     /**
@@ -89,15 +68,8 @@ object TellMessagesMgr {
      */
     @JvmStatic
     fun save(file: String, messages: List<TellMessage?>?) {
-        try {
-            BufferedOutputStream(Files.newOutputStream(Paths.get(file))).use { bos ->
-                ObjectOutputStream(bos).use { output ->
-                    if (logger.isDebugEnabled) logger.debug("Saving the messages.")
-                    output.writeObject(messages)
-                }
-            }
-        } catch (e: IOException) {
-            logger.error("Unable to save messages queue.", e)
+        if (messages != null) {
+            saveData(file, messages, logger, "messages")
         }
     }
 }
diff --git a/src/test/kotlin/net/thauvin/erik/mobibot/commands/InfoTest.kt b/src/test/kotlin/net/thauvin/erik/mobibot/commands/InfoTest.kt
index f2036da..67ad8c8 100644
--- a/src/test/kotlin/net/thauvin/erik/mobibot/commands/InfoTest.kt
+++ b/src/test/kotlin/net/thauvin/erik/mobibot/commands/InfoTest.kt
@@ -46,6 +46,8 @@ class InfoTest {
         assertThat(1320300000L.toUptime(), "weeks days hours minutes").isEqualTo("2 weeks 1 day 6 hours 45 minutes")
         assertThat(2700000L.toUptime(), "45 minutes").isEqualTo("45 minutes")
         assertThat(60000L.toUptime(), "1 minute").isEqualTo("1 minute")
-        assertThat(0L.toUptime(), "0 minute").isEqualTo("0 minute")
+        assertThat(59000L.toUptime(), "59 seconds").isEqualTo("59 seconds")
+        assertThat(0L.toUptime(), "0 second").isEqualTo("0 second")
+
     }
 }
diff --git a/src/test/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenTest.kt b/src/test/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenTest.kt
new file mode 100644
index 0000000..3e28f32
--- /dev/null
+++ b/src/test/kotlin/net/thauvin/erik/mobibot/commands/seen/SeenTest.kt
@@ -0,0 +1,75 @@
+/*
+ * SeenTest.kt
+ *
+ * Copyright (c) 2004-2022, Erik C. Thauvin (erik@thauvin.net)
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   Redistributions of source code must retain the above copyright notice, this
+ *   list of conditions and the following disclaimer.
+ *
+ *   Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ *
+ *   Neither the name of this project nor the names of its contributors may be
+ *   used to endorse or promote products derived from this software without
+ *   specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+ * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package net.thauvin.erik.mobibot.commands.seen
+
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isGreaterThan
+import assertk.assertions.isTrue
+import org.testng.annotations.AfterClass
+import org.testng.annotations.BeforeClass
+import org.testng.annotations.Test
+import kotlin.io.path.deleteIfExists
+import kotlin.io.path.fileSize
+
+class SeenTest {
+    private val tmpFile = kotlin.io.path.createTempFile(suffix = ".ser")
+    private val seen = Seen(tmpFile.toAbsolutePath().toString())
+
+    @BeforeClass
+    fun saveTest() {
+        seen.add("ErikT")
+        assertThat(tmpFile.fileSize(), "temporary file is empty").isGreaterThan(0)
+    }
+
+    @AfterClass(alwaysRun = true)
+    fun afterClass() {
+        tmpFile.deleteIfExists()
+    }
+
+    @Test
+    fun loadTest() {
+        val nick = seen.seenNicks[0]
+        seen.clear()
+        seen.load()
+        assertThat(seen.seenNicks[0] == nick, "nick is different").isTrue()
+    }
+
+    @Test(priority = 10)
+    fun clearTest() {
+        seen.clear()
+        seen.save()
+        seen.load()
+        assertThat(seen.seenNicks.size, "nicknames are not empty.").isEqualTo(0)
+    }
+}