diff --git a/.travis.yml b/.travis.yml
index 072f8da..c8ce000 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,8 +2,11 @@
 
 language: objective-c
 os: osx
+# Add a TEST_DIR=[directory] row for each library (or group of libraries) to test
+# Each will be run as an independent, hermetic test (in parallel when resources permit)
+# on Traivs.
 env:
-  - USING_OS=osx USING_XCODE=6.1
+  - TEST_DIR=gson
 
 branches:
   only:
@@ -16,7 +19,8 @@ sudo: false
 install:
   - export TERM=dumb
   - env
-  - if [ "$USING_OS" = "osx" ]; then (/usr/libexec/java_home -v 1.7 -F -V); fi
+  - xcrun clang -v
+  - /usr/libexec/java_home -v 1.7 -F -V
   - java -Xmx32m -version && javac -J-Xmx32m -version
   - pushd j2objc-gradle
   - ./gradlew wrapper
@@ -24,6 +28,10 @@ install:
   # In this repo, building of the j2objc-gradle plugin is just preperation.
   - ./gradlew build
   - popd
+  - pushd libraryBuilds
+  # Downloads and configures j2objc distribution.
+  - ./prep.sh
 
+# Note the install prep leaves us in the libraryBuilds directory.
 script:
-  - echo TODO Run some e2e tests.
+  - ./run-test.sh $TEST_DIR
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 0000000..38c24f2
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,49 @@
+Please keep in mind that your "Contribution(s)" are submitted under
+the [Apache 2.0 License](LICENSE).
+
+#### Updating j2objc-gradle
+The version of j2objc-gradle in this repo is not automatically kept up
+to date with master of https://github.com/j2objc-contrib/j2objc-gradle.
+
+As a submodule, you can update j2objc-gradle by doing:
+
+```shell
+# (start with a clean git working directory)
+# (from your local repo for this project)
+git checkout -b update-plugin
+pushd j2objc-gradle
+git pull
+popd
+git add .
+git commit -m 'Updating j2objc-gradle to HEAD'
+# (submit the update-plugin branch as a PR to the repo)
+```
+
+Make sure this PR is seperate from any other work.  If a library you want
+to build depends on the update, work in a new branch parented to the commit
+above.
+
+#### Library build verification
+
+On OS X we have system tests under the `libraryBuilds` directory.  Each test directory
+has one root Gradle project (and zero or more subprojects), some or all of which apply the
+`j2objc-gradle` plugin.  Locally you can run them as follows:
+
+```sh
+# Once per git repository and/or new release of j2objc, run prep.
+pushd libraryBuilds && ./prep.sh && popd
+# This downloads j2objc and prepares the environment.
+
+# Every time you want to run the build tests:
+./gradlew build && pushd systemTests && ./run-all.sh && popd
+# Normal Gradle build results will be displayed for each test project.
+```
+
+These system tests are also run as part of OS X continuous integration builds on Travis.
+You are not required to run the system tests locally before creating a PR (they can take
+time and processing power), however if the tests fail on Travis you will need to update
+the PR until they pass.
+
+When you add a new library to build, make sure it is referenced in run-all.sh (for
+human contributors) and in .travis.yml (for continuous builds).
+
diff --git a/libraryBuilds/.gitignore b/libraryBuilds/.gitignore
new file mode 100644
index 0000000..9723eb9
--- /dev/null
+++ b/libraryBuilds/.gitignore
@@ -0,0 +1,8 @@
+# Ignore all the wrappers below.
+gradle/
+gradlew.bat
+# Under this directory, we do in fact need to preserve local.properties!
+!local.properties
+# Generated by prep.sh
+common/local.properties
+localJ2objcDist/
diff --git a/libraryBuilds/gson/build.gradle b/libraryBuilds/gson/build.gradle
new file mode 100644
index 0000000..657321f
--- /dev/null
+++ b/libraryBuilds/gson/build.gradle
@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) 2015 the authors of j2objc-common-libs-e2e-test
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+buildscript {
+    repositories {
+        jcenter()
+    }
+    dependencies {
+        // This is the build output of the plugin itself.
+        classpath fileTree(dir: '../../j2objc-gradle/build/libs', include: ['*.jar'])
+    }
+}
+
+apply plugin: 'java'
+apply plugin: 'com.github.j2objccontrib.j2objcgradle'
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    j2objcTranslation 'com.google.code.gson:gson:2.3.1:sources'
+}
+
+j2objcConfig {
+    filenameCollisionCheck false
+
+    // Almost always there are no tests provided in an external source jar.
+    testMinExpectedTests 0
+    finalConfigure()
+}
diff --git a/libraryBuilds/gson/gradlew b/libraryBuilds/gson/gradlew
new file mode 120000
index 0000000..bde144b
--- /dev/null
+++ b/libraryBuilds/gson/gradlew
@@ -0,0 +1 @@
+../../j2objc-gradle/gradlew
\ No newline at end of file
diff --git a/libraryBuilds/gson/local.properties b/libraryBuilds/gson/local.properties
new file mode 120000
index 0000000..217624b
--- /dev/null
+++ b/libraryBuilds/gson/local.properties
@@ -0,0 +1 @@
+../common/local.properties
\ No newline at end of file
diff --git a/libraryBuilds/prep.sh b/libraryBuilds/prep.sh
new file mode 100755
index 0000000..c974a2d
--- /dev/null
+++ b/libraryBuilds/prep.sh
@@ -0,0 +1,34 @@
+#!/bin/bash
+#
+# Copyright (c) 2015 the authors of j2objc-common-libs-e2e-test
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+J2OBJC_VERSION=0.9.8.1
+mkdir localJ2objcDist
+mkdir common
+
+# Fail if any command fails
+set -ev
+
+pushd localJ2objcDist
+
+# For developer local testing, don't keep redownloading the zip file.
+if [ ! -e j2objcDist.zip ]; then
+  curl -L https://github.com/google/j2objc/releases/download/$J2OBJC_VERSION/j2objc-$J2OBJC_VERSION.zip > j2objcDist.zip
+  unzip j2objcDist.zip
+  mv j2objc-$J2OBJC_VERSION j2objcDist
+  echo j2objc.home=$PWD/j2objcDist > ../common/local.properties
+fi
+
+popd
diff --git a/libraryBuilds/run-all.sh b/libraryBuilds/run-all.sh
new file mode 100755
index 0000000..019e216
--- /dev/null
+++ b/libraryBuilds/run-all.sh
@@ -0,0 +1,20 @@
+#!/bin/bash
+#
+# Copyright (c) 2015 the authors of j2objc-common-libs-e2e-test
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Fail if anything fails.
+set -ev
+
+./run-test.sh gson
diff --git a/libraryBuilds/run-test.sh b/libraryBuilds/run-test.sh
new file mode 100755
index 0000000..9fb30d1
--- /dev/null
+++ b/libraryBuilds/run-test.sh
@@ -0,0 +1,26 @@
+#!/bin/bash
+#
+# Copyright (c) 2015 the authors of j2objc-common-libs-e2e-test
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Fail if anything fails.
+set -ev
+
+TEST_DIR=$1
+echo Running test $TEST_DIR
+pushd $TEST_DIR
+./gradlew wrapper
+./gradlew clean
+./gradlew build
+popd