We have a test suite that can run (thanks to achen's start)

tests/AndroidManifest.xml

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+<?xml version="1.0" encoding="utf-8"?>
+<!-- package name must be unique so suffix with "tests" so package loader doesn't ignore us -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android"
+          package="com.fsck.k9.tests"
+          android:versionCode="1"
+          android:versionName="1.0">
+    <!-- We add an application tag here just so that we can indicate that
+         this package needs to link against the android.test library,
+         which is needed when building test cases. -->
+    <application>
+        <uses-library android:name="android.test.runner" />
+    </application>
+    <!--
+    This declares that this application uses the instrumentation test runner targeting
+    the package of com.fsck.k9.  To run the tests use the command:
+    "adb shell am instrument -w com.fsck.k9.tests/android.test.InstrumentationTestRunner"
+    -->
+    <instrumentation android:name="android.test.InstrumentationTestRunner"
+                     android:targetPackage="com.fsck.k9"
+                     android:label="Tests for com.fsck.k9"/>
+</manifest>

tests/build.properties

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+# This file is used to override default values used by the Ant build system.
+#
+# This file must be checked in Version Control Systems, as it is
+# integral to the build system of your project.
+
+# This file is only used by the Ant script.
+
+# You can use this to override default values such as
+#  'source.dir' for the location of your java source folder and
+#  'out.dir' for the location of your output folder.
+
+# You can also use it define how the release builds are signed by declaring
+# the following properties:
+#  'key.store' for the location of your keystore and
+#  'key.alias' for the name of the key to use.
+# The password will be asked during the build when you use the 'release' target.
+
+tested.project.dir=../

tests/build.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<project name="K9Test" default="help">
+
+<!-- The local.properties file is created and updated by the 'android'
+     tool.
+     It contains the path to the SDK. It should *NOT* be checked into
+     Version Control Systems. -->
+    <property file="local.properties" />
+
+    <!-- The build.properties file can be created by you and is never touched
+         by the 'android' tool. This is the place to change some of the
+         default property values used by the Ant rules.
+         Here are some properties you may want to change/update:
+
+         source.dir
+             The name of the source directory. Default is 'src'.
+         out.dir
+             The name of the output directory. Default is 'bin'.
+
+         Properties related to the SDK location or the project target should
+         be updated using the 'android' tool with the 'update' action.
+
+         This file is an integral part of the build system for your
+         application and should be checked into Version Control Systems.
+
+         -->
+    <property file="build.properties" />
+
+    <!-- The default.properties file is created and updated by the 'android'
+         tool, as well as ADT.
+         This file is an integral part of the build system for your
+         application and should be checked into Version Control Systems. -->
+    <property file="default.properties" />
+
+    <!-- Custom Android task to deal with the project target, and import the
+         proper rules.
+         This requires ant 1.6.0 or above. -->
+    <path id="android.antlibs">
+        <pathelement path="${sdk.dir}/tools/lib/anttasks.jar" />
+        <pathelement path="${sdk.dir}/tools/lib/sdklib.jar" />
+        <pathelement path="${sdk.dir}/tools/lib/androidprefs.jar" />
+    </path>
+
+    <taskdef name="setup"
+        classname="com.android.ant.SetupTask"
+        classpathref="android.antlibs" />
+
+<!-- extension targets. Uncomment the ones where you want to do custom work
+     in between standard targets -->
+<!--
+    <target name="-pre-build">
+    </target>
+    <target name="-pre-compile">
+    </target>
+
+    [This is typically used for code obfuscation.
+     Compiled code location: ${out.classes.absolute.dir}
+     If this is not done in place, override ${out.dex.input.absolute.dir}]
+    <target name="-post-compile">
+    </target>
+-->
+
+
+    <!-- Execute the Android Setup task that will setup some properties
+         specific to the target, and import the build rules files.
+
+         The rules file is imported from
+            <SDK>/platforms/<target_platform>/ant/ant_rules_r#.xml
+
+         To customize existing targets, there are two options:
+         - Customize only one target:
+             - copy/paste the target into this file, *before* the
+               <setup> task.
+             - customize it to your needs.
+         - Customize the whole script.
+             - copy/paste the content of the rules files (minus the top node)
+               into this file, *after* the <setup> task
+             - disable the import of the rules by changing the setup task
+               below to <setup import="false" />.
+             - customize to your needs.
+    -->
+    <setup />
+
+</project>

tests/default.properties

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+# This file is automatically generated by Android Tools.
+# Do not modify this file -- YOUR CHANGES WILL BE ERASED!
+#
+# This file must be checked in Version Control Systems.
+#
+# To customize properties used by the Ant build system use,
+# "build.properties", and override values to adapt the script to your
+# project structure.
+
+# Project target.
+target=android-9

tests/proguard.cfg

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+-optimizationpasses 5
+-dontusemixedcaseclassnames
+-dontskipnonpubliclibraryclasses
+-dontpreverify
+-verbose
+-optimizations !code/simplification/arithmetic,!field/*,!class/merging/*
+
+-keep public class * extends android.app.Activity
+-keep public class * extends android.app.Application
+-keep public class * extends android.app.Service
+-keep public class * extends android.content.BroadcastReceiver
+-keep public class * extends android.content.ContentProvider
+-keep public class * extends android.app.backup.BackupAgentHelper
+-keep public class * extends android.preference.Preference
+-keep public class com.android.vending.licensing.ILicensingService
+
+-keepclasseswithmembernames class * {
+    native <methods>;
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet);
+}
+
+-keepclasseswithmembernames class * {
+    public <init>(android.content.Context, android.util.AttributeSet, int);
+}
+
+-keepclassmembers enum * {
+    public static **[] values();
+    public static ** valueOf(java.lang.String);
+}
+
+-keep class * implements android.os.Parcelable {
+  public static final android.os.Parcelable$Creator *;
+}

tests/src/com/fsck/k9/activity/AccountsTest.java

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+package com.fsck.k9;
+
+import android.test.ActivityInstrumentationTestCase2;
+import com.fsck.k9.activity.Accounts;
+/**
+ * This is a simple framework for a test of an Application.  See
+ * {@link android.test.ApplicationTestCase ApplicationTestCase} for more information on
+ * how to write and extend Application tests.
+ * <p/>
+ * To run this test, you can type:
+ * adb shell am instrument -w \
+ * -e class com.fsck.k9.activity.AccountsTest \
+ * com.fsck.k9.tests/android.test.InstrumentationTestRunner
+ */
+public class AccountsTest extends ActivityInstrumentationTestCase2<Accounts> {
+
+    public AccountsTest() {
+        super("com.fsck.k9", Accounts.class);
+    }
+
+}