Add test for query command

Make a request by piping a query to STDIN and check that the response is
rendered as JSON. I used tab indentation in the query and response
because my editor wanted to and there was a risk of mixing spaces/tabs
in future changes. The example GraphQL query and response are stolen
from here:

- https://graphql.org/learn/queries/

cmd/query_test.go

@@ -0,0 +1,103 @@
+package cmd_test
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"net/http"
+	"os"
+	"os/exec"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+	"github.com/onsi/gomega/gexec"
+	"github.com/onsi/gomega/ghttp"
+)
+
+var _ = Describe("Query", func() {
+	var (
+		server   *ghttp.Server
+		token    string
+		tempHome string
+		stdin    bytes.Buffer
+		command  *exec.Cmd
+	)
+
+	BeforeEach(func() {
+		server = ghttp.NewServer()
+
+		var err error
+		tempHome, err = ioutil.TempDir("", "circleci-cli-test-")
+		Expect(err).ToNot(HaveOccurred())
+
+		token = "mytoken"
+		command = exec.Command(pathCLI, "query",
+			"-t", token,
+			"-e", server.URL(),
+		)
+		command.Stdin = &stdin
+		command.Env = append(os.Environ(),
+			fmt.Sprintf("HOME=%s", tempHome),
+			fmt.Sprintf("USERPROFILE=%s", tempHome), // windows
+		)
+	})
+
+	AfterEach(func() {
+		server.Close()
+		Expect(os.RemoveAll(tempHome)).To(Succeed())
+	})
+
+	Describe("query provided to STDIN", func() {
+		var responseData string
+
+		BeforeEach(func() {
+			query := `query {
+	hero {
+		name
+		friends {
+			name
+		}
+	}
+}
+`
+			responseData = `{
+	"hero": {
+		"name": "R2-D2",
+		"friends": [
+			{
+				"name": "Luke Skywalker"
+			},
+			{
+				"name": "Han Solo"
+			},
+			{
+				"name": "Leia Organa"
+			}
+		]
+	}
+}
+`
+			server.AppendHandlers(
+				ghttp.CombineHandlers(
+					ghttp.VerifyRequest("POST", "/"),
+					ghttp.VerifyHeader(http.Header{
+						"Authorization": []string{token},
+					}),
+					ghttp.RespondWith(http.StatusOK, `{"data": `+responseData+`}`),
+				),
+			)
+
+			_, err := stdin.WriteString(query)
+			Expect(err).ToNot(HaveOccurred())
+		})
+
+		It("should make request and return result as JSON", func() {
+			session, err := gexec.Start(command, GinkgoWriter, GinkgoWriter)
+			Expect(err).ShouldNot(HaveOccurred())
+			session.Wait()
+			Eventually(session.Err.Contents()).Should(BeEmpty())
+			Eventually(session.Out.Contents()).Should(MatchJSON(responseData))
+			Eventually(session).Should(gexec.Exit(0))
+		})
+	})
+})