Add unit tests for initializing the client.

Signed-off-by: Daniel Nephin <dnephin@docker.com>

cli/command/cli_test.go

@@ -0,0 +1,57 @@
+package command
+
+import (
+	"os"
+	"testing"
+
+	"github.com/docker/cli/cli/config/configfile"
+	"github.com/docker/cli/cli/flags"
+	"github.com/docker/docker/api"
+	"github.com/docker/docker/client"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestNewAPIClientFromFlags(t *testing.T) {
+	host := "unix://path"
+	opts := &flags.CommonOptions{Hosts: []string{host}}
+	configFile := &configfile.ConfigFile{
+		HTTPHeaders: map[string]string{
+			"My-Header": "Custom-Value",
+		},
+	}
+	apiclient, err := NewAPIClientFromFlags(opts, configFile)
+	require.NoError(t, err)
+	assert.Equal(t, host, apiclient.DaemonHost())
+
+	expectedHeaders := map[string]string{
+		"My-Header":  "Custom-Value",
+		"User-Agent": UserAgent(),
+	}
+	assert.Equal(t, expectedHeaders, apiclient.(*client.Client).CustomHTTPHeaders())
+	assert.Equal(t, api.DefaultVersion, apiclient.ClientVersion())
+}
+
+func TestNewAPIClientFromFlagsWithAPIVersionFromEnv(t *testing.T) {
+	customVersion := "v3.3.3"
+	defer patchEnvVariable(t, "DOCKER_API_VERSION", customVersion)()
+
+	opts := &flags.CommonOptions{}
+	configFile := &configfile.ConfigFile{}
+	apiclient, err := NewAPIClientFromFlags(opts, configFile)
+	require.NoError(t, err)
+	assert.Equal(t, customVersion, apiclient.ClientVersion())
+}
+
+// TODO: move to gotestyourself
+func patchEnvVariable(t *testing.T, key, value string) func() {
+	oldValue, ok := os.LookupEnv(key)
+	require.NoError(t, os.Setenv(key, value))
+	return func() {
+		if !ok {
+			require.NoError(t, os.Unsetenv(key))
+			return
+		}
+		require.NoError(t, os.Setenv(key, oldValue))
+	}
+}