diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5c0bb83..ba4c489 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 - refactor `shared_set_tpm_path_constant` function
 - move all instructions to `docs/` dir
 - add `bin/install_plugins` cli executable script
+- improved test runner function
 
 ### v2.0.0, 2015-07-07
 - enable overriding default key bindings
diff --git a/tests/helpers.sh b/tests/helpers.sh
index 122347a..3bc0cfa 100644
--- a/tests/helpers.sh
+++ b/tests/helpers.sh
@@ -63,3 +63,11 @@ exit_value_helper() {
 		exit 0
 	fi
 }
+
+run_tests() {
+	# get all the functions starting with 'test_' and invoke them
+	for test in $(compgen -A function | grep "^test_"); do
+		"$test"
+	done
+	exit_value_helper
+}
diff --git a/tests/test_plugin_clean.sh b/tests/test_plugin_clean.sh
index d47564a..af6c660 100755
--- a/tests/test_plugin_clean.sh
+++ b/tests/test_plugin_clean.sh
@@ -27,8 +27,4 @@ test_plugin_installation() {
 	teardown_helper
 }
 
-main() {
-	test_plugin_installation
-	exit_value_helper
-}
-main
+run_tests
diff --git a/tests/test_plugin_installation.sh b/tests/test_plugin_installation.sh
index 3953a84..2aaf1fa 100755
--- a/tests/test_plugin_installation.sh
+++ b/tests/test_plugin_installation.sh
@@ -4,6 +4,8 @@ CURRENT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 PLUGINS_DIR="$HOME/.tmux/plugins"
 TPM_DIR="$PWD"
 
+CUSTOM_PLUGINS_DIR="$HOME/foo/plugins"
+
 source "$CURRENT_DIR/helpers.sh"
 
 # TMUX KEY-BINDING TESTS
@@ -14,17 +16,33 @@ test_plugin_installation_via_tmux_key_binding() {
 	run-shell "$TPM_DIR/tpm"
 	HERE
 
-	# opens tmux and test it with `expect`
-	"$CURRENT_DIR"/expect_successful_plugin_download ||
+	"$CURRENT_DIR/expect_successful_plugin_download" ||
 		fail_helper "[key-binding] plugin installation fails"
 
-	# check plugin dir exists after download
 	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
 		fail_helper "[key-binding] plugin download fails"
 
 	teardown_helper
 }
 
+test_plugin_installation_custom_dir_via_tmux_key_binding() {
+	set_tmux_conf_helper <<- HERE
+	set-environment -g TMUX_PLUGIN_MANAGER_PATH '$CUSTOM_PLUGINS_DIR'
+
+	set -g @plugin "tmux-plugins/tmux-example-plugin"
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	"$CURRENT_DIR/expect_successful_plugin_download" ||
+		fail_helper "[key-binding][custom dir] plugin installation fails"
+
+	check_dir_exists_helper "$CUSTOM_PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[key-binding][custom dir] plugin download fails"
+
+	teardown_helper
+	rm -rf "$CUSTOM_PLUGINS_DIR"
+}
+
 test_multiple_plugins_installation_via_tmux_key_binding() {
 	set_tmux_conf_helper <<- HERE
 	set -g @plugin "tmux-plugins/tmux-example-plugin"
@@ -33,7 +51,7 @@ test_multiple_plugins_installation_via_tmux_key_binding() {
 	HERE
 
 	# opens tmux and test it with `expect`
-	"$CURRENT_DIR"/expect_successful_multiple_plugins_download ||
+	"$CURRENT_DIR/expect_successful_multiple_plugins_download" ||
 		fail_helper "[key-binding] multiple plugins installation fails"
 
 	check_dir_exists_helper "$PLUGINS_DIR/tmux-example-plugin/" ||
@@ -65,6 +83,27 @@ test_plugin_installation_via_script() {
 	teardown_helper
 }
 
+test_plugin_installation_custom_dir_via_script() {
+	set_tmux_conf_helper <<- HERE
+	set-environment -g TMUX_PLUGIN_MANAGER_PATH '$CUSTOM_PLUGINS_DIR'
+
+	set -g @plugin "tmux-plugins/tmux-example-plugin"
+	run-shell "$TPM_DIR/tpm"
+	HERE
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" '"tmux-example-plugin" download success' ||
+		fail_helper "[script][custom dir] plugin installation fails"
+
+	check_dir_exists_helper "$CUSTOM_PLUGINS_DIR/tmux-example-plugin/" ||
+		fail_helper "[script][custom dir] plugin download fails"
+
+	script_run_helper "$TPM_DIR/bin/install_plugins" 'Already installed "tmux-example-plugin"' ||
+		fail_helper "[script][custom dir] plugin already installed message fail"
+
+	teardown_helper
+	rm -rf "$CUSTOM_PLUGINS_DIR"
+}
+
 test_multiple_plugins_installation_via_script() {
 	set_tmux_conf_helper <<- HERE
 	set -g @plugin "tmux-plugins/tmux-example-plugin"
@@ -87,13 +126,4 @@ test_multiple_plugins_installation_via_script() {
 	teardown_helper
 }
 
-main() {
-	test_plugin_installation_via_tmux_key_binding
-	test_multiple_plugins_installation_via_tmux_key_binding
-
-	test_plugin_installation_via_script
-	test_multiple_plugins_installation_via_script
-
-	exit_value_helper
-}
-main
+run_tests
diff --git a/tests/test_plugin_installation_legacy.sh b/tests/test_plugin_installation_legacy.sh
index d0bf375..f14725f 100755
--- a/tests/test_plugin_installation_legacy.sh
+++ b/tests/test_plugin_installation_legacy.sh
@@ -92,13 +92,4 @@ test_legacy_and_new_syntax_for_plugin_installation_work_via_script() {
 	teardown_helper
 }
 
-main() {
-	test_plugin_installation_via_tmux_key_binding
-	test_legacy_and_new_syntax_for_plugin_installation_work_via_tmux_key_binding
-
-	test_plugin_installation_via_script
-	test_legacy_and_new_syntax_for_plugin_installation_work_via_script
-
-	exit_value_helper
-}
-main
+run_tests
diff --git a/tests/test_plugin_sourcing.sh b/tests/test_plugin_sourcing.sh
index 73956c7..b77c07f 100755
--- a/tests/test_plugin_sourcing.sh
+++ b/tests/test_plugin_sourcing.sh
@@ -28,8 +28,4 @@ test_plugin_sourcing() {
 	teardown_helper
 }
 
-main() {
-	test_plugin_sourcing
-	exit_value_helper
-}
-main
+run_tests
diff --git a/tests/test_plugin_update.sh b/tests/test_plugin_update.sh
index bc9e8e2..b70fca8 100755
--- a/tests/test_plugin_update.sh
+++ b/tests/test_plugin_update.sh
@@ -30,8 +30,4 @@ test_plugin_installation() {
 	teardown_helper
 }
 
-main() {
-	test_plugin_installation
-	exit_value_helper
-}
-main
+run_tests