Add a test for aria2c

Author: yyuu

Diff for: test/fetch.bats

@@ -19,6 +19,20 @@ setup() {
   assert_output_contains "error: failed to download package-1.0.0.tar.gz"
 }
 
+@test "using aria2c if available" {
+  stub aria2c "* -o * http://example.com/* : cp $FIXTURE_ROOT/\${4##*/} \$3"
+
+  install_fixture definitions/without-checksum
+  assert_success
+  assert_output <<OUT
+Downloading package-1.0.0.tar.gz...
+-> http://example.com/packages/package-1.0.0.tar.gz
+Installing package-1.0.0...
+Installed package-1.0.0 to ${TMP}/install
+OUT
+  unstub aria2c
+}
+
 @test "fetching from git repository" {
   stub git "clone --depth 1 --branch master http://example.com/packages/package.git package-dev : mkdir package-dev"