libmachine/provision: add test for DockerClientVersion

Signed-off-by: Peter Schultz <peter.schultz@classmarkets.com>

libmachine/provision/utils.go

@@ -274,15 +274,15 @@ func WaitForDocker(p Provisioner, dockerPort int) error {
 }
 
 // DockerClientVersion returns the version of the Docker client on the host
-// that is provisioned by p, e.g. "1.12.1".
-func DockerClientVersion(p Provisioner) (string, error) {
+// that ssh is connected to, e.g. "1.12.1".
+func DockerClientVersion(ssh SSHCommander) (string, error) {
 	// `docker version --format {{.Client.Version}}` would be preferrable, but
 	// that fails if the server isn't running yet.
 	//
 	// output is expected to be something like
 	//
 	//     Docker version 1.12.1, build 7a86f89
-	output, err := p.SSHCommand("docker --version")
+	output, err := ssh.SSHCommand("docker --version")
 	if err != nil {
 		return "", err
 	}

libmachine/provision/utils_test.go

@@ -208,3 +208,29 @@ func TestGetFilesystemType(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, "btrfs", fsType)
 }
+
+func TestDockerClientVersion(t *testing.T) {
+	cases := []struct {
+		output, want string
+	}{
+		{"Docker version 1.9.1, build a34a1d5\n", "1.9.1"},
+		{"Docker version 1.9.1\n", "1.9.1"},
+		{"Docker version 1.13.0-rc1, build deadbeef\n", "1.13.0-rc1"},
+		{"Docker version 1.13.0-dev, build deadbeef\n", "1.13.0-dev"},
+	}
+
+	sshCmder := &provisiontest.FakeSSHCommander{
+		Responses: make(map[string]string),
+	}
+
+	for _, tc := range cases {
+		sshCmder.Responses["docker --version"] = tc.output
+		got, err := DockerClientVersion(sshCmder)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if got != tc.want {
+			t.Errorf("Unexpected version string from %q; got %q, want %q", tc.output, tc.want, got)
+		}
+	}
+}