diff --git a/pom.xml b/pom.xml
index 0710a38..5d28d8a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -134,6 +134,11 @@
       <artifactId>byte-buddy</artifactId>
       <version>1.14.13</version>
     </dependency>
+    <dependency>
+      <groupId>org.codehaus.groovy</groupId>
+      <artifactId>groovy</artifactId>
+      <version>3.0.17</version>
+    </dependency>
   </dependencies>
 
   <build>
diff --git a/src/main/java/ru/ewc/checklogic/FileStateFactory.java b/src/main/java/ru/ewc/checklogic/FileStateFactory.java
index 2b62497..05d309d 100644
--- a/src/main/java/ru/ewc/checklogic/FileStateFactory.java
+++ b/src/main/java/ru/ewc/checklogic/FileStateFactory.java
@@ -29,12 +29,14 @@
 import java.io.OutputStream;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
+import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import lombok.SneakyThrows;
 import org.yaml.snakeyaml.Yaml;
+import ru.ewc.checklogic.testing.FunctionsLocator;
 import ru.ewc.decisions.api.InMemoryLocator;
 import ru.ewc.decisions.api.Locator;
 import ru.ewc.state.State;
@@ -65,9 +67,19 @@ public State initialState() {
         this.locators.clear();
         this.loadLocatorsFromApplicationConfig();
         this.loadInMemoryRequestLocator();
+        this.loadFunctionsLocator();
         return new State(this.locators);
     }
 
+    private void loadFunctionsLocator() {
+        this.locators.add(
+            new FunctionsLocator(
+                this.config.functionsLocatorName(),
+                Paths.get(this.config.getRoot(), "functions")
+            )
+        );
+    }
+
     private void loadInMemoryRequestLocator() {
         this.locators.add(
             new InMemoryLocator(this.config.requestLocatorName(), new HashMap<>())
diff --git a/src/main/java/ru/ewc/checklogic/ServerConfiguration.java b/src/main/java/ru/ewc/checklogic/ServerConfiguration.java
index e4b352f..addb02b 100644
--- a/src/main/java/ru/ewc/checklogic/ServerConfiguration.java
+++ b/src/main/java/ru/ewc/checklogic/ServerConfiguration.java
@@ -48,7 +48,8 @@ public ServerConfiguration(final String root) {
         this.parameters = new HashMap<>(
             Map.of(
                 "request", "request",
-                "command", "available"
+                "command", "available",
+                "function", "function"
             )
         );
     }
@@ -88,4 +89,8 @@ public Path applicationConfig() {
     public String getRoot() {
         return this.root;
     }
+
+    public String functionsLocatorName() {
+        return this.parameters.get("function");
+    }
 }
diff --git a/src/main/java/ru/ewc/checklogic/testing/FunctionsLocator.java b/src/main/java/ru/ewc/checklogic/testing/FunctionsLocator.java
new file mode 100644
index 0000000..8261047
--- /dev/null
+++ b/src/main/java/ru/ewc/checklogic/testing/FunctionsLocator.java
@@ -0,0 +1,92 @@
+/*
+ * MIT License
+ *
+ * Copyright (c) 2024 Decision-Driven Development
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package ru.ewc.checklogic.testing;
+
+import groovy.lang.Binding;
+import groovy.util.GroovyScriptEngine;
+import java.net.URL;
+import java.nio.file.Path;
+import java.util.HashMap;
+import lombok.SneakyThrows;
+import ru.ewc.decisions.api.ComputationContext;
+import ru.ewc.decisions.api.DecitaException;
+import ru.ewc.decisions.api.InMemoryLocator;
+import ru.ewc.decisions.api.Locator;
+
+/**
+ * I am a special locator that can load functions from Groovy scripts. My main responsibility is to
+ * run the Groovy script and return the result of the script execution.
+ *
+ * @since 0.4.1
+ */
+public final class FunctionsLocator implements Locator {
+    /**
+     * The locator's name.
+     */
+    private final String name;
+
+    /**
+     * The in-memory locator used to store overridden values.
+     */
+    private final InMemoryLocator locator;
+
+    /**
+     * Groovy script engine used to run the Groovy scripts.
+     */
+    private final GroovyScriptEngine engine;
+
+    @SneakyThrows
+    public FunctionsLocator(final String name, final Path path) {
+        this.name = name;
+        this.locator = new InMemoryLocator("locator", new HashMap<>());
+        this.engine = new GroovyScriptEngine(new URL[]{path.toUri().toURL()});
+    }
+
+    @SneakyThrows
+    @Override
+    public String fragmentBy(
+        final String fragment,
+        final ComputationContext context
+    ) throws DecitaException {
+        final String result;
+        if (this.locator.state().containsKey(fragment)) {
+            result = this.locator.fragmentBy(fragment, context);
+        } else {
+            final Binding binding = new Binding();
+            binding.setVariable("context", context);
+            result = this.engine.run("%s.groovy".formatted(fragment), binding).toString();
+        }
+        return result;
+    }
+
+    @Override
+    public void setFragmentValue(final String fragment, final String value) {
+        this.locator.setFragmentValue(fragment, value);
+    }
+
+    @Override
+    public String locatorName() {
+        return this.name;
+    }
+}