diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..6946830
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,3 @@
+test-runner.sh
+test/assert.sh
+test/stub.sh
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..0cd9f49
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,15 @@
+language: c
+env:
+  - TMUX_VERSION="1.6"
+  - TMUX_VERSION="1.7"
+  - TMUX_VERSION="1.8"
+  - TMUX_VERSION="1.9a"
+before_install:
+  - sudo apt-get update
+  - sudo apt-get install -y bc build-essential libevent-dev libncurses5-dev
+  - wget http://downloads.sourceforge.net/tmux/tmux-${TMUX_VERSION}.tar.gz
+  - tar -zxf tmux-${TMUX_VERSION}.tar.gz
+  - cd tmux-${TMUX_VERSION}
+  - ./configure && make && sudo make install
+  - cd ..
+script: make test
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..8a83c37
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,50 @@
+test: bootstrap
+	./test-runner.sh
+
+bootstrap: test-runner.sh test/assert.sh test/stub.sh
+clean: remove_test-runner.sh remove_test/assert.sh remove_test/stub.sh
+update: update_test-runner.sh update_test/assert.sh update_test/stub.sh
+
+test-runner.sh:
+	echo "fetching test-runner.sh..." && \
+	curl -s -L -o test-runner.sh \
+		https://github.com/jimeh/test-runner.sh/raw/v0.2.0/test-runner.sh && \
+	chmod +x test-runner.sh
+
+remove_test-runner.sh:
+	( \
+		test -f "test-runner.sh" && rm "test-runner.sh" && \
+		echo "removed test-runner.sh"\
+	) || exit 0
+
+update_test-runner.sh: remove_test-runner.sh test-runner.sh
+
+test/assert.sh:
+	echo "fetching test/assert.sh..." && \
+	curl -s -L -o test/assert.sh \
+		https://raw.github.com/lehmannro/assert.sh/v1.0.2/assert.sh
+
+remove_test/assert.sh:
+	test -f "test/assert.sh" && \
+		rm "test/assert.sh" && \
+		echo "removed test/assert.sh"
+
+update_test/assert.sh: remove_test/assert.sh test/assert.sh
+
+test/stub.sh:
+	echo "fetching test/stub.sh..." && \
+	curl -s -L -o test/stub.sh \
+		https://raw.github.com/jimeh/stub.sh/v1.0.1/stub.sh
+
+remove_test/stub.sh:
+	test -f "test/stub.sh" && \
+		rm "test/stub.sh" && \
+		echo "removed test/stub.sh"
+
+update_test/stub.sh: remove_test/stub.sh test/stub.sh
+
+.SILENT:
+.PHONY: test bootstrap clean \
+	remove_test-runner.sh update_test-runner.sh \
+	remove_test/assert.sh update_test/assert.sh \
+	remove_test/stub.sh   update_test/stub.sh
diff --git a/test/lib/env.test.sh b/test/lib/env.test.sh
new file mode 100755
index 0000000..0caf1c0
--- /dev/null
+++ b/test/lib/env.test.sh
@@ -0,0 +1,33 @@
+#! /usr/bin/env bash
+source "../test-helper.sh"
+
+#
+# env.sh tests.
+#
+
+# Setup.
+realTMUXIFIER="$TMUXIFIER"
+TMUXIFER="/path/to/tmuxifier"
+
+# When TMUXIFIER_LAYOUT_PATH is not set.
+source "${root}/lib/env.sh"
+assert 'echo $TMUXIFIER_LAYOUT_PATH' "${TMUXIFIER}/layouts"
+
+# When TMUXIFIER_LAYOUT_PATH is set and has a trailing slash.
+TMUXIFIER_LAYOUT_PATH="/path/to/layouts/"
+source "${root}/lib/env.sh"
+assert 'echo $TMUXIFIER_LAYOUT_PATH' "/path/to/layouts"
+unset TMUXIFIER_LAYOUT_PATH
+
+# When TMUXIFIER_LAYOUT_PATH is set and does not have a trailing slash.
+TMUXIFIER_LAYOUT_PATH="/path/to/layouts"
+source "${root}/lib/env.sh"
+assert 'echo $TMUXIFIER_LAYOUT_PATH' "/path/to/layouts"
+unset TMUXIFIER_LAYOUT_PATH
+
+# Tear down.
+TMUXIFER="$realTMUXIFIER"
+unset realTMUXIFIER
+
+# End of tests.
+assert_end "env.sh"
diff --git a/test/lib/layout-helpers/__expand_path.test.sh b/test/lib/layout-helpers/__expand_path.test.sh
new file mode 100755
index 0000000..f94069f
--- /dev/null
+++ b/test/lib/layout-helpers/__expand_path.test.sh
@@ -0,0 +1,27 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# __expand_path() tests.
+#
+
+# Setup.
+realHOME="$HOME"
+HOME="/home/test-user"
+
+# When given a path containing "~", it expands "~" to "$HOME".
+assert '__expand_path "~/Foo/Bar"' "${HOME}/Foo/Bar"
+
+# When given a path without "~", it returns path as is.
+assert '__expand_path "/path/to/file"' "/path/to/file"
+
+# When given a path containing spaces, it returns path correctly.
+assert '__expand_path "~/Path To/File"' "${HOME}/Path To/File"
+
+# Tear down.
+HOME="$realHOME"
+unset realHOME
+
+# End of tests.
+assert_end "__expand_path()"
diff --git a/test/lib/layout-helpers/__get_first_window_index.test.sh b/test/lib/layout-helpers/__get_first_window_index.test.sh
new file mode 100755
index 0000000..c08dfd4
--- /dev/null
+++ b/test/lib/layout-helpers/__get_first_window_index.test.sh
@@ -0,0 +1,30 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# __get_first_window_index() tests.
+#
+
+# When first window has a index of 0.
+create-test-session
+assert "__get_first_window_index" "0"
+kill-test-session
+
+# When first window has a index of 1.
+create-test-session
+test-socket-tmux new-window -t "$session:1"
+test-socket-tmux kill-window -t "$session:0"
+assert "__get_first_window_index" "1"
+kill-test-session
+
+# When first window has a index of 2.
+create-test-session
+test-socket-tmux new-window -t "$session:2"
+test-socket-tmux kill-window -t "$session:0"
+assert "__get_first_window_index" "2"
+kill-test-session
+
+
+# End of tests.
+assert_end "__get_first_window_index()"
diff --git a/test/lib/layout-helpers/__go_to_session.test.sh b/test/lib/layout-helpers/__go_to_session.test.sh
new file mode 100755
index 0000000..84e4a89
--- /dev/null
+++ b/test/lib/layout-helpers/__go_to_session.test.sh
@@ -0,0 +1,32 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# __go_to_session() tests.
+#
+
+# Setup.
+session="tmuxifier-test-session"
+
+# When TMUX is not set, attach to $session.
+stub tmuxifier-tmux
+__go_to_session
+assert_raises \
+  "stub_called_with tmuxifier-tmux -u attach-session -t \"${session}:\"" 0
+restore tmuxifier-tmux
+
+# When TMUX is set, switch to $session.
+TMUX="/tmp/tmux-501/default,1203,0"
+stub tmuxifier-tmux
+__go_to_session
+assert_raises \
+  "stub_called_with tmuxifier-tmux -u switch-client -t \"${session}:\"" 0
+restore tmuxifier-tmux
+unset TMUX
+
+# Tear down.
+unset session
+
+# End of tests.
+assert_end "__go_to_session()"
diff --git a/test/lib/layout-helpers/__go_to_window_or_session_path.test.sh b/test/lib/layout-helpers/__go_to_window_or_session_path.test.sh
new file mode 100755
index 0000000..4d6542f
--- /dev/null
+++ b/test/lib/layout-helpers/__go_to_window_or_session_path.test.sh
@@ -0,0 +1,49 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# __go_to_window_or_session_path() tests.
+#
+
+# When neither $window_root or $session_root are set, does nothing.
+stub run_cmd
+__go_to_window_or_session_path
+assert "stub_called_times run_cmd" "0"
+restore run_cmd
+
+
+# When only $window_root is set, runs cd to $window_root path.
+stub run_cmd
+window_root="/tmp"
+__go_to_window_or_session_path
+assert 'stub_called_with_times run_cmd cd \"/tmp\"' "1"
+assert 'stub_called_with_times run_cmd clear' "1"
+unset window_root
+restore run_cmd
+
+
+# When only $session_root is set, runs cd to $session_root path.
+stub run_cmd
+session_root="/usr"
+__go_to_window_or_session_path
+assert 'stub_called_with_times run_cmd cd \"/usr\"' "1"
+assert 'stub_called_with_times run_cmd clear' "1"
+unset session_root
+restore run_cmd
+
+
+# When $window_root and $session_root are set, runs cd to $window_root path.
+stub run_cmd
+window_root="/tmp"
+session_root="/usr"
+__go_to_window_or_session_path
+assert 'stub_called_with_times run_cmd cd \"/tmp\"' "1"
+assert 'stub_called_with_times run_cmd clear' "1"
+unset window_root
+unset session_root
+restore run_cmd
+
+
+# End of tests.
+assert_end "__go_to_window_or_session_path()"
diff --git a/test/lib/layout-helpers/new_window.test.sh b/test/lib/layout-helpers/new_window.test.sh
new file mode 100755
index 0000000..5b162b7
--- /dev/null
+++ b/test/lib/layout-helpers/new_window.test.sh
@@ -0,0 +1,47 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# new_window() tests.
+#
+
+# When called without arguments, creates new window.
+create-test-session
+stub __go_to_window_or_session_path
+assert "test-socket-window-count" "1"
+new_window
+assert "test-socket-window-count" "2"
+assert "stub_called_times __go_to_window_or_session_path" "1"
+restore __go_to_window_or_session_path
+kill-test-session
+
+# When called with name argument, creates new window with specified name.
+create-test-session
+stub __go_to_window_or_session_path
+assert "test-socket-window-count yippieezzz" "0"
+new_window "yippieezzz"
+assert "test-socket-window-count" "2"
+assert "test-socket-window-count yippieezzz" "1"
+restore __go_to_window_or_session_path
+kill-test-session
+
+# When called with name and command argument, creates new window with
+# specified name and executes given command.
+rm "/tmp/tmuxifier-new_window-test" &> /dev/null
+create-test-session
+stub __go_to_window_or_session_path
+new_window "foobardoo" "touch /tmp/tmuxifier-new_window-test; bash"
+assert "test-socket-window-count" "2"
+assert "test-socket-window-count foobardoo" "1"
+assert_raises 'test -f "/tmp/tmuxifier-new_window-test"' 0
+restore __go_to_window_or_session_path
+kill-test-session
+rm "/tmp/tmuxifier-new_window-test" &> /dev/null
+
+
+# Tear down.
+kill-test-server
+
+# End of tests.
+assert_end "new_window()"
diff --git a/test/lib/layout-helpers/tmux.test.sh b/test/lib/layout-helpers/tmux.test.sh
new file mode 100755
index 0000000..2803b22
--- /dev/null
+++ b/test/lib/layout-helpers/tmux.test.sh
@@ -0,0 +1,20 @@
+#! /usr/bin/env bash
+source "../../test-helper.sh"
+source "${root}/lib/layout-helpers.sh"
+
+#
+# tmux() tests.
+#
+
+# Passes all arguments to tmuxifier-tmux.
+stub tmuxifier-tmux
+tmux -V
+tmux --help
+tmux new -s dude
+assert_raises "stub_called_with tmuxifier-tmux -V" 0
+assert_raises "stub_called_with tmuxifier-tmux --help" 0
+assert_raises "stub_called_with tmuxifier-tmux new -s dude" 0
+restore tmuxifier-tmux
+
+# End of tests.
+assert_end "tmux()"
diff --git a/test/lib/runtime.test.sh b/test/lib/runtime.test.sh
new file mode 100755
index 0000000..06d5a68
--- /dev/null
+++ b/test/lib/runtime.test.sh
@@ -0,0 +1,23 @@
+#! /usr/bin/env bash
+source "../test-helper.sh"
+
+#
+# runtime.sh tests.
+#
+
+source "${root}/lib/runtime.sh"
+
+# We assume env.sh has been sourced if $TMUXIFIER_LAYOUT_PATH has been set.
+assert 'echo $TMUXIFIER_LAYOUT_PATH' "${TMUXIFIER}/layouts"
+
+# We ensure $session_root is set to $HOME by default.
+assert 'echo $session_root' "$HOME"
+
+# We assume layout-helpers.sh has been sourced if a few of them are available.
+for helper in new_window split_v split_h select_window select_pane; do
+  assert "type $helper | head -1" "$helper is a function"
+done
+
+
+# End of tests.
+assert_end "runtime.sh"
diff --git a/test/lib/util.test.sh b/test/lib/util.test.sh
new file mode 100755
index 0000000..df6cc08
--- /dev/null
+++ b/test/lib/util.test.sh
@@ -0,0 +1,58 @@
+#! /usr/bin/env bash
+source "../test-helper.sh"
+source "${root}/lib/util.sh"
+
+#
+# calling-help() tests.
+#
+
+# Returns 0 when "--help" is part of passed arguments.
+assert_raises 'calling-help --help' 0
+assert_raises 'calling-help foo --help' 0
+assert_raises 'calling-help --help bar' 0
+assert_raises 'calling-help foo --help bar' 0
+
+# Returns 0 when "-h" is part of passed arguments.
+assert_raises 'calling-help -h' 0
+assert_raises 'calling-help foo -h' 0
+assert_raises 'calling-help -h bar' 0
+assert_raises 'calling-help foo -h bar' 0
+
+# Returns 1 when neither "--help" or "-h" is not part of passed arguments.
+assert_raises 'calling-help' 1
+assert_raises 'calling-help foo' 1
+assert_raises 'calling-help foo bar' 1
+
+# Returns 1 when "--help" is part of passed arguments, but not free-standing.
+assert_raises 'calling-help --help-me' 1
+assert_raises 'calling-help foo--help' 1
+
+# Returns 1 when "-h" is part of passed arguments, but not free-standing.
+assert_raises 'calling-help -hj' 1
+assert_raises 'calling-help welcome-home' 1
+
+# End of tests.
+assert_end "calling-help()"
+
+
+#
+# calling-complete() tests.
+#
+
+# Returns 0 when "--complete" is part of passed arguments.
+assert_raises 'calling-complete --complete' 0
+assert_raises 'calling-complete foo --complete' 0
+assert_raises 'calling-complete --complete bar' 0
+assert_raises 'calling-complete foo --complete bar' 0
+
+# Returns 1 when "--complete" is not part of passed arguments.
+assert_raises 'calling-complete' 1
+assert_raises 'calling-complete foo' 1
+assert_raises 'calling-complete foo bar' 1
+
+# Returns 1 when "--complete" is part of passed arguments, but not free-standing.
+assert_raises 'calling-complete --complete-me' 1
+assert_raises 'calling-complete foo--complete' 1
+
+# End of tests.
+assert_end "calling-complete()"
diff --git a/test/libexec/tmuxifier-tmux.test.sh b/test/libexec/tmuxifier-tmux.test.sh
new file mode 100755
index 0000000..9716360
--- /dev/null
+++ b/test/libexec/tmuxifier-tmux.test.sh
@@ -0,0 +1,22 @@
+#! /usr/bin/env bash
+source "../test-helper.sh"
+source "${root}/lib/util.sh"
+
+#
+# tmuxifier-tmux tests.
+#
+
+# Setup.
+libexec="${root}/libexec"
+test-socket-tmux new-session -d -s foobar
+test-socket-tmux new-session -d -s dude
+
+# Passes all arguments to Tmux.
+assert "${libexec}/tmuxifier-tmux list-sessions -F \"- #{session_name}\"" \
+       "- dude\n- foobar"
+
+# Tear down.
+kill-test-server
+
+# End of tests.
+assert_end "tmuxifier-tmux"
diff --git a/test/test-helper.sh b/test/test-helper.sh
new file mode 100644
index 0000000..ed081be
--- /dev/null
+++ b/test/test-helper.sh
@@ -0,0 +1,87 @@
+[ -n "$TEST_DEBUG" ] && set -x
+
+resolve_link() {
+  $(type -p greadlink readlink | head -1) $1
+}
+
+abs_dirname() {
+  local cwd="$(pwd)"
+  local path="$1"
+
+  while [ -n "$path" ]; do
+    cd "${path%/*}"
+    local name="${path##*/}"
+    path="$(resolve_link "$name" || true)"
+  done
+
+  pwd
+  cd "$cwd"
+}
+
+# Find and store path to Tmux binary.
+TMUX_BIN="$(command -v tmux)"
+
+# Set testroot variable.
+testroot="$(abs_dirname "$BASH_SOURCE")"
+
+# Set root variable.
+root="$(abs_dirname "$testroot/../..")"
+
+# Set TMUXIFIER environment variable.
+TMUXIFIER="$root"
+
+# Setup PATH environment variable.
+PATH="$root/bin:$root/libexec:$PATH"
+
+# Unset TMUX environment variable, tests assume they're not running within
+# Tmux.
+unset TMUX
+
+# Unset various Tmuxifier environment variables to prevent a local install of
+# Tmuxifier interfering with tests.
+unset TMUXIFIER_LAYOUT_PATH
+unset TMUXIFIER_TMUX_OPTS
+unset TMUXIFIER_NO_COMPLETE
+
+# Include assert.sh and stub.sh libraries.
+source "${testroot}/assert.sh"
+source "${testroot}/stub.sh"
+
+
+#
+# Test Helpers
+#
+
+test-socket-tmux() {
+  export TMUXIFIER_TMUX_OPTS="-L tmuxifier-tests"
+  "$TMUX_BIN" $TMUXIFIER_TMUX_OPTS $@
+}
+
+create-test-session() {
+  session="$1"
+  if [ -z "$session" ]; then session="test"; fi
+
+  test-socket-tmux new-session -d -s "$session"
+}
+
+kill-test-session() {
+  local target="$1"
+  if [ -z "$target" ]; then target="$session"; fi
+
+  test-socket-tmux kill-session -t "$target"
+}
+
+kill-test-server() {
+  test-socket-tmux kill-server
+  unset TMUXIFIER_TMUX_OPTS
+  unset session
+}
+
+test-socket-window-count() {
+  local list="$(test-socket-tmux list-windows)"
+  if [ -n "$1" ]; then
+    echo "$list" | grep $1 | wc -l | awk '{print $1}'
+  else
+    echo "$list" | wc -l | awk '{print $1}'
+  fi
+}