diff --git a/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineConfigurationTest.java b/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineConfigurationTest.java
new file mode 100644
index 0000000..91cbcfe
--- /dev/null
+++ b/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineConfigurationTest.java
@@ -0,0 +1,87 @@
+package de.staropensource.sosengine.base.srctests;
+
+import de.staropensource.sosengine.base.EngineConfiguration;
+import de.staropensource.sosengine.unittests.UnitLogger;
+import org.joor.Reflect;
+import org.junit.jupiter.api.*;
+
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Properties;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Tests the class {@link EngineConfiguration}.
+ */
+@SuppressWarnings("unused")
+@DisplayName("EngineConfiguration")
+class EngineConfigurationTest {
+    /**
+     * The unit logger for this instance.
+     */
+    private final UnitLogger logger = new UnitLogger(getClass());
+
+    /**
+     * Initializes the {@link EngineConfiguration} class before each test.
+     */
+    @BeforeEach
+    void initializeClass() {
+        new EngineConfiguration();
+    }
+
+    /**
+     * Sets the {@link EngineConfiguration} {@code instance} to {@code null} after each test.
+     */
+    @AfterEach
+    void clearClass() {
+        Reflect.on(EngineConfiguration.getInstance()).set("instance", null);
+    }
+
+    /**
+     * Tests the method {@code loadConfiguration}.
+     */
+    @Test
+    @DisplayName("Method loadConfiguration")
+    void testLoadConfiguration() {
+        logger.testCall("testLoadConfiguration");
+
+        EngineConfiguration config = EngineConfiguration.getInstance();
+        String group = EngineConfiguration.getGroup();
+        String[] keys = new String[]{
+                "debug",
+                "debugShortcodeConverter",
+                "errorShortcodeConverter",
+                "loggerLevel",
+                "loggerTemplate"
+        };
+        Map<String, Object> defaultValues = new HashMap<>();
+
+        // Load default configuration
+        config.loadDefaultConfiguration();
+
+        // Save default values
+        for (String setting : keys)
+            defaultValues.put(setting, config.getSetting(setting));
+
+        // Load custom configuration
+        Properties properties = new Properties();
+
+        properties.setProperty(group + "debug", "true");
+        properties.setProperty(group + "debugShortcodeConverter", "true");
+        properties.setProperty(group + "errorShortcodeConverter", "false");
+        properties.setProperty(group + "loggerLevel", "diagnostic");
+        properties.setProperty(group + "loggerTemplate", "%log_path% says: %message%");
+
+        config.loadConfiguration(properties);
+
+        // Compare custom values against default ones
+        for (String setting : keys) {
+            Object defaultValue = defaultValues.get(setting);
+            Object customValue = config.getSetting(setting);
+
+            logger.diag("Comparing setting " + setting);
+            assertNotEquals(defaultValue, customValue);
+        }
+    }
+}
diff --git a/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineTest.java b/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineTest.java
new file mode 100644
index 0000000..20bcab6
--- /dev/null
+++ b/base/src/test/java/de/staropensource/sosengine/base/srctests/EngineTest.java
@@ -0,0 +1,31 @@
+package de.staropensource.sosengine.base.srctests;
+
+import de.staropensource.sosengine.base.Engine;
+import de.staropensource.sosengine.unittests.UnitLogger;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Tests the class {@link EngineTest}.
+ */
+@SuppressWarnings("unused")
+@DisplayName("Engine")
+class EngineTest {
+    /**
+     * The {@link UnitLogger} for this instance.
+     */
+    private final UnitLogger logger = new UnitLogger(getClass());
+
+    /**
+     * Tests the constructor.
+     */
+    @Test
+    @DisplayName("Constructor")
+    void testConstructor() {
+        logger.testCall("testConstructor");
+
+        assertNotEquals(new Engine(), null, "Engine should not be null");
+    }
+}
diff --git a/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/MiscellaneousTest.java b/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/MiscellaneousTest.java
new file mode 100644
index 0000000..37b776c
--- /dev/null
+++ b/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/MiscellaneousTest.java
@@ -0,0 +1,39 @@
+package de.staropensource.sosengine.base.srctests.utility;
+
+import de.staropensource.sosengine.base.utility.Miscellaneous;
+import de.staropensource.sosengine.unittests.UnitLogger;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Tests the class {@link Miscellaneous}.
+ */
+@SuppressWarnings("unused")
+@DisplayName("Miscellaneous")
+class MiscellaneousTest {
+    /**
+     * The {@link UnitLogger} for this instance.
+     */
+    private final UnitLogger logger = new UnitLogger(getClass());
+
+    /**
+     * Tests the method {@code padNumbers}.
+     */
+    @ParameterizedTest
+    @DisplayName("padNumbers")
+    @CsvSource({
+            "5, 3, 005",
+            "15, 2, 15",
+            "666, 2, 666",
+            "5918, 6, 005918",
+            "5819853, 10, 0005819853"
+    })
+    void testPadNumbers(int number, int length, String expected) {
+        logger.testCall("testPadNumbers", number, length, expected);
+        String result = Miscellaneous.padNumbers(number, length);
+        assertEquals(result, expected, "Result \"" + result + "\" does not match expected output \"" + expected + "\"");
+    }
+}
diff --git a/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/PlaceholderEngineTest.java b/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/PlaceholderEngineTest.java
new file mode 100644
index 0000000..d2ec108
--- /dev/null
+++ b/base/src/test/java/de/staropensource/sosengine/base/srctests/utility/PlaceholderEngineTest.java
@@ -0,0 +1,66 @@
+package de.staropensource.sosengine.base.srctests.utility;
+
+import de.staropensource.sosengine.base.classes.Placeholder;
+import de.staropensource.sosengine.base.utility.PlaceholderEngine;
+import de.staropensource.sosengine.unittests.UnitLogger;
+import org.jetbrains.annotations.NotNull;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Tests the class {@link PlaceholderEngine}.
+ */
+@SuppressWarnings("unused")
+@DisplayName("PlaceholderEngine")
+class PlaceholderEngineTest {
+    /**
+     * The {@link UnitLogger} for this instance.
+     */
+    private final UnitLogger logger = new UnitLogger(getClass());
+
+    /**
+     * Tests the method {@code process}.
+     */
+    @ParameterizedTest
+    @DisplayName("process")
+    @CsvSource({
+            "Test placeholder %test%,   Test placeholder TEST",
+            "%invalid% must be invalid, %invalid% must be invalid",
+            "This %status%!,             This works!"
+    })
+    void testProcess(String text, String expected) {
+        logger.testCall("testProcess", text, expected);
+
+        List<Placeholder> placeholders = new ArrayList<>();
+        placeholders.add(new Placeholder() {
+            @Override
+            public @NotNull String getName() {
+                return "test";
+            }
+            @Override
+            public @NotNull String replace(@NotNull String text) {
+                return text.replace("%" + getName() + "%", "TEST");
+            }
+        });
+        placeholders.add(new Placeholder() {
+            @Override
+            public @NotNull String getName() {
+                return "status";
+            }
+            @Override
+            public @NotNull String replace(@NotNull String text) {
+                return text.replace("%" + getName() + "%", "works");
+            }
+        });
+
+        text = PlaceholderEngine.getInstance().process(text, placeholders);
+
+        assertEquals(text, expected);
+    }
+}