Remove Guice to fix flaky tests

donkey/build.gradle

@@ -1,6 +1,17 @@
 // Donkey: the message engine. Produces donkey-model.jar and
 // donkey-server.jar in donkey/setup (mirrors donkey/build.xml).
 
+apply plugin: 'java-test-fixtures'
+
+// The test-fixtures plugin gives the test source set the main classes through
+// a dependency on this project, which the non-transitive test classpaths
+// drop, so add them back directly. Remove this when transitive resolution
+// is enabled.
+sourceSets.test {
+    compileClasspath += sourceSets.main.output
+    runtimeClasspath += sourceSets.main.output
+}
+
 dependencies {
     implementation libs.bundles.donkey.main
     testImplementation libs.bundles.donkey.test

donkey/src/main/java/com/mirth/connect/donkey/server/Donkey.java

@@ -23,7 +23,6 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
-import com.google.inject.Inject;
 import com.mirth.connect.donkey.model.DatabaseConstants;
 import com.mirth.connect.donkey.server.channel.Channel;
 import com.mirth.connect.donkey.server.controllers.ChannelController;
@@ -39,7 +38,6 @@
 import com.mirth.connect.donkey.util.xstream.XStreamSerializer;
 
 public class Donkey {
-    @Inject
     private static Donkey instance;
 
     public static Donkey getInstance() {

donkey/src/main/java/com/mirth/connect/donkey/server/DonkeyConnectionPools.java

@@ -15,7 +15,6 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
-import com.google.inject.Inject;
 import com.mirth.connect.donkey.model.DatabaseConstants;
 import com.mirth.connect.donkey.server.data.jdbc.ConnectionPool;
 import com.mirth.connect.donkey.server.data.jdbc.HikariConnectionPool;
@@ -24,7 +23,6 @@ public class DonkeyConnectionPools {
 
     private static final Logger logger = LogManager.getLogger(DonkeyConnectionPools.class);
 
-    @Inject
     private static volatile DonkeyConnectionPools instance = null;
 
     private ConnectionPool connectionPool;

donkey/src/main/java/com/mirth/connect/donkey/server/controllers/ChannelController.java

@@ -17,7 +17,6 @@
 
 import org.apache.commons.lang3.StringUtils;
 
-import com.google.inject.Inject;
 import com.mirth.connect.donkey.model.channel.Ports;
 import com.mirth.connect.donkey.model.message.Status;
 import com.mirth.connect.donkey.server.Donkey;
@@ -27,7 +26,6 @@
 import com.mirth.connect.donkey.server.data.DonkeyDaoFactory;
 
 public class ChannelController {
-    @Inject
     private static ChannelController instance;
 
     public static ChannelController getInstance() {

donkey/src/main/java/com/mirth/connect/donkey/server/controllers/MessageController.java

@@ -18,7 +18,6 @@
 import org.apache.commons.collections4.CollectionUtils;
 import org.apache.commons.collections4.MapUtils;
 
-import com.google.inject.Inject;
 import com.mirth.connect.donkey.model.message.ConnectorMessage;
 import com.mirth.connect.donkey.model.message.Message;
 import com.mirth.connect.donkey.model.message.Status;
@@ -30,7 +29,6 @@
 import com.mirth.connect.donkey.util.StringUtil;
 
 public class MessageController {
-    @Inject
     private static MessageController instance;
 
     public static MessageController getInstance() {

donkey/src/test/java/com/mirth/connect/donkey/server/channel/ChannelTest.java

@@ -25,14 +25,12 @@
 import java.util.UUID;
 import java.util.concurrent.atomic.AtomicLong;
 
+import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
 import org.mockito.invocation.InvocationOnMock;
 import org.mockito.stubbing.Answer;
 
-import com.google.inject.AbstractModule;
-import com.google.inject.Guice;
-import com.google.inject.Injector;
 import com.mirth.connect.donkey.model.channel.ConnectorProperties;
 import com.mirth.connect.donkey.model.channel.SourceConnectorProperties;
 import com.mirth.connect.donkey.model.channel.SourceConnectorPropertiesInterface;
@@ -44,28 +42,31 @@
 import com.mirth.connect.donkey.server.event.EventDispatcher;
 import com.mirth.connect.donkey.server.message.DataType;
 import com.mirth.connect.donkey.server.queue.SourceQueue;
+import com.mirth.connect.donkey.testing.StaticOverride;
 import com.mirth.connect.donkey.util.SerializerProvider;
 
 public class ChannelTest {
 
+    private static StaticOverride donkeyOverride;
+
     @BeforeClass
     public static void setupControllers() throws Exception {
         Donkey donkey = mock(Donkey.class);
         when(donkey.getEventDispatcher()).thenReturn(mock(EventDispatcher.class));
 
-        Injector injector = Guice.createInjector(new AbstractModule() {
-            @Override
-            protected void configure() {
-                requestStaticInjection(Donkey.class);
-                bind(Donkey.class).toInstance(donkey);
-            }
-        });
-        injector.getInstance(Donkey.class);
+        donkeyOverride = StaticOverride.install(Donkey.class, "instance", donkey);
 
         // Make sure injection succeeded
         assertTrue(donkey == Donkey.getInstance());
     }
 
+    @AfterClass
+    public static void restoreDonkey() {
+        if (donkeyOverride != null) {
+            donkeyOverride.close();
+        }
+    }
+
     @Test
     public void testRawMessageWithAttachments() throws Exception {
         Channel channel = createChannel();

donkey/src/test/java/com/mirth/connect/donkey/testing/StaticOverrideTest.java

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: MPL-2.0
+// SPDX-FileCopyrightText: 2026 Tony Germano <tony@germano.name>
+
+package com.mirth.connect.donkey.testing;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertThrows;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.After;
+import org.junit.Test;
+
+public class StaticOverrideTest {
+
+    private static class Holder {
+        private static String instance;
+        private static volatile String volatileInstance;
+        private static final String CONSTANT = "constant";
+        private String nonStatic;
+    }
+
+    @After
+    public void reset() {
+        Holder.instance = null;
+        Holder.volatileInstance = null;
+    }
+
+    @Test
+    public void installsAndRestoresPreviousValue() throws Exception {
+        Holder.instance = "original";
+
+        AutoCloseable handle = StaticOverride.install(Holder.class, "instance", "replacement");
+        assertEquals("replacement", Holder.instance);
+
+        handle.close();
+        assertEquals("original", Holder.instance);
+    }
+
+    @Test
+    public void restoresNull() throws Exception {
+        AutoCloseable handle = StaticOverride.install(Holder.class, "instance", "replacement");
+        handle.close();
+
+        assertNull(Holder.instance);
+    }
+
+    @Test
+    public void worksOnVolatileField() throws Exception {
+        try (AutoCloseable handle = StaticOverride.install(Holder.class, "volatileInstance", "replacement")) {
+            assertEquals("replacement", Holder.volatileInstance);
+        }
+
+        assertNull(Holder.volatileInstance);
+    }
+
+    @Test
+    public void nestedOverridesRestoreInOrder() throws Exception {
+        Holder.instance = "original";
+
+        AutoCloseable outer = StaticOverride.install(Holder.class, "instance", "outer");
+        AutoCloseable inner = StaticOverride.install(Holder.class, "instance", "inner");
+
+        inner.close();
+        assertEquals("outer", Holder.instance);
+        outer.close();
+        assertEquals("original", Holder.instance);
+    }
+
+    @Test
+    public void secondCloseDoesNothing() throws Exception {
+        Holder.instance = "original";
+        AutoCloseable handle = StaticOverride.install(Holder.class, "instance", "replacement");
+        handle.close();
+
+        Holder.instance = "set later";
+        handle.close();
+
+        assertEquals("set later", Holder.instance);
+    }
+
+    @Test
+    public void closeFailsWhenValueWasReplaced() throws Exception {
+        AutoCloseable handle = StaticOverride.install(Holder.class, "instance", "replacement");
+        Holder.instance = "someone else";
+
+        assertThrows(IllegalStateException.class, handle::close);
+        assertEquals("someone else", Holder.instance);
+    }
+
+    @Test
+    public void closingOutOfOrderFails() throws Exception {
+        AutoCloseable outer = StaticOverride.install(Holder.class, "instance", "outer");
+        StaticOverride.install(Holder.class, "instance", "inner");
+
+        assertThrows(IllegalStateException.class, outer::close);
+    }
+
+    @Test
+    public void rejectsFinalField() {
+        assertThrows(IllegalArgumentException.class, () -> StaticOverride.install(Holder.class, "CONSTANT", "x"));
+        assertSame("constant", Holder.CONSTANT);
+    }
+
+    @Test
+    public void rejectsNonStaticField() {
+        assertThrows(IllegalArgumentException.class, () -> StaticOverride.install(Holder.class, "nonStatic", "x"));
+    }
+
+    @Test
+    public void rejectsMissingField() {
+        IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () -> StaticOverride.install(Holder.class, "missing", "x"));
+        assertTrue(e.getCause() instanceof NoSuchFieldException);
+    }
+
+    @Test
+    public void rejectsWrongType() {
+        assertThrows(IllegalArgumentException.class, () -> StaticOverride.install(Holder.class, "instance", 42));
+        assertNull(Holder.instance);
+    }
+}

donkey/src/testFixtures/java/com/mirth/connect/donkey/testing/StaticOverride.java

@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: MPL-2.0
+// SPDX-FileCopyrightText: 2026 Tony Germano <tony@germano.name>
+
+package com.mirth.connect.donkey.testing;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.Modifier;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+/**
+ * Temporarily replaces the value of a static field, such as a singleton instance, for the duration
+ * of a test.
+ */
+public final class StaticOverride implements AutoCloseable {
+    private final Class<?> owner;
+    private final Field field;
+    private final Object value;
+    private final Object previous;
+    private final AtomicBoolean closed = new AtomicBoolean();
+
+    private StaticOverride(Class<?> owner, Field field, Object value, Object previous) {
+        this.owner = owner;
+        this.field = field;
+        this.value = value;
+        this.previous = previous;
+    }
+
+    /**
+     * Sets a static field to {@code value} until the returned handle is closed, then puts the
+     * previous value back. Closing more than once does nothing.
+     *
+     * @throws IllegalArgumentException
+     *             if the field does not exist, is not a non-final static field, or cannot hold
+     *             {@code value}
+     */
+    public static StaticOverride install(Class<?> owner, String fieldName, Object value) {
+        Field field;
+        try {
+            field = owner.getDeclaredField(fieldName);
+        } catch (NoSuchFieldException e) {
+            throw new IllegalArgumentException(owner.getName() + " has no field named " + fieldName, e);
+        }
+
+        int modifiers = field.getModifiers();
+        if (!Modifier.isStatic(modifiers) || Modifier.isFinal(modifiers)) {
+            throw new IllegalArgumentException(owner.getName() + "." + fieldName + " is not a non-final static field");
+        }
+        field.setAccessible(true);
+
+        synchronized (owner) {
+            Object previous = get(field);
+            set(field, value);
+            return new StaticOverride(owner, field, value, previous);
+        }
+    }
+
+    /**
+     * Puts back the value the field had before this override was installed.
+     *
+     * @throws IllegalStateException
+     *             if something else replaced the field's value after this override was installed
+     */
+    @Override
+    public void close() {
+        if (!closed.compareAndSet(false, true)) {
+            return;
+        }
+
+        synchronized (owner) {
+            Object current = get(field);
+            if (current != value) {
+                throw new IllegalStateException(owner.getName() + "." + field.getName() + " was replaced by " + current + " while " + value + " was installed");
+            }
+            set(field, previous);
+        }
+    }
+
+    private static Object get(Field field) {
+        try {
+            return field.get(null);
+        } catch (IllegalAccessException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    private static void set(Field field, Object value) {
+        try {
+            field.set(null, value);
+        } catch (IllegalAccessException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+}

gradle/libs.versions.toml

@@ -123,7 +123,6 @@ glassfish-ha-api = { module = "org.glassfish.ha:ha-api", version = "3.1.9" }
 glassfish-management-api = { module = "org.glassfish.external:management-api", version = "3.2.1-b001" }
 gmbal-api-only = { module = "org.glassfish.gmbal:gmbal-api-only", version = "3.1.0-b001" }
 guava = { module = "com.google.guava:guava", version = "32.0.1-jre" }
-guice = { module = "com.google.inject:guice", version = "4.1.0" }
 hamcrest = { module = "org.hamcrest:hamcrest", version = "2.2" }
 hapi-structures-v27 = { module = "ca.uhn.hapi:hapi-structures-v27", version.ref = "hapi" }
 hapi-structures-v28 = { module = "ca.uhn.hapi:hapi-structures-v28", version.ref = "hapi" }
@@ -413,7 +412,6 @@ donkey-main = [
     "error-prone-annotations",
     "failureaccess",
     "guava",
-    "guice",
     "hikaricp",
     "j2objc-annotations",
     "javassist",
@@ -542,7 +540,6 @@ server-main = [
     "glassfish-ha-api",
     "glassfish-management-api",
     "gmbal-api-only",
-    "guice",
     "hapi-structures-v27",
     "hapi-structures-v28",
     "hapi-structures-v281",

gradle/vendored-layout.json

@@ -130,7 +130,6 @@
   "com.google.guava:failureaccess": "guava",
   "com.google.guava:guava": "guava",
   "com.google.guava:listenablefuture": "guava",
-  "com.google.inject:guice": "",
   "com.google.j2objc:j2objc-annotations": "guava",
   "com.microsoft.sqlserver:mssql-jdbc": "database",
   "com.mysql:mysql-connector-j": "database",
@@ -183,7 +182,6 @@
   "com.github.mwiede:jsch": "",
   "com.github.oshi:oshi-core": "",
   "com.github.zafarkhaja:java-semver": "",
-  "com.google.inject:guice": "",
   "com.microsoft.sqlserver:mssql-jdbc": "database",
   "com.mysql:mysql-connector-j": "database",
   "com.oracle.database.jdbc:ojdbc8": "database",