test, integration: Add cluster primitives to integration framework

This further extends the integration framework to add some simple
primitives for building clusters. More complex primitives and patterns
can be added in the future, but this should serve the general cases.

integration/basic_test.go

@@ -128,3 +128,125 @@ func TestInstance1(t *testing.T) {
 		})
 	}
 }
+
+func TestCluster0(t *testing.T) {
+	// TODO: implement a simple test for documentation purposes
+}
+
+func TestCluster1(t *testing.T) {
+	type test struct { // an individual test
+		name   string
+		code   string // mcl code
+		fail   bool
+		hosts  []string
+		expect map[string]map[string]string // hostname, file, contents
+	}
+	values := []test{}
+
+	{
+		code := Code(`
+		$root = getenv("MGMT_TEST_ROOT")
+
+		file "${root}/mgmt-hostname" {
+			content => "i am ${hostname()}\n",
+			state => "exists",
+		}
+		`)
+		values = append(values, test{
+			name:  "simple pair",
+			code:  code,
+			fail:  false,
+			hosts: []string{"h1", "h2"},
+			expect: map[string]map[string]string{
+				"h1": {
+					"mgmt-hostname": "i am h1\n",
+				},
+				"h2": {
+					"mgmt-hostname": "i am h2\n",
+				},
+			},
+		})
+	}
+	{
+		code := Code(`
+		$root = getenv("MGMT_TEST_ROOT")
+
+		file "${root}/mgmt-hostname" {
+			content => "i am ${hostname()}\n",
+			state => "exists",
+		}
+		`)
+		values = append(values, test{
+			name:  "hello world",
+			code:  code,
+			fail:  false,
+			hosts: []string{"h1", "h2", "h3"},
+			expect: map[string]map[string]string{
+				"h1": {
+					"mgmt-hostname": "i am h1\n",
+				},
+				"h2": {
+					"mgmt-hostname": "i am h2\n",
+				},
+				"h3": {
+					"mgmt-hostname": "i am h3\n",
+				},
+			},
+		})
+	}
+
+	for index, test := range values { // run all the tests
+		t.Run(fmt.Sprintf("test #%d (%s)", index, test.name), func(t *testing.T) {
+			code, fail, hosts, expect := test.code, test.fail, test.hosts, test.expect
+
+			c := Cluster{
+				Hostnames: hosts,
+				Preserve:  true,
+			}
+			err := c.SimpleDeployLang(code)
+			if d := c.Dir(); d != "" {
+				t.Logf("test ran in:\n%s", d)
+			}
+
+			if !fail && err != nil {
+				t.Errorf("failed with: %+v", err)
+				return
+			}
+			if fail && err == nil {
+				t.Errorf("passed, expected fail")
+				return
+			}
+
+			if expect == nil { // test done early
+				return
+			}
+
+			instances := c.Instances()
+			for _, h := range hosts {
+				instance := instances[h]
+				d := instance.Dir()
+				hexpect, exists := expect[h]
+				if !exists {
+					continue
+				}
+
+				files := []string{}
+				for x := range hexpect {
+					files = append(files, x)
+				}
+				sort.Strings(files) // loop in a deterministic order
+				for _, f := range files {
+					filename := path.Join(d, RootDirectory, f)
+					b, err := ioutil.ReadFile(filename)
+					if err != nil {
+						t.Errorf("could not read file: `%s`", filename)
+						continue
+					}
+					if hexpect[f] != string(b) {
+						t.Errorf("file: `%s` did not match expected", f)
+					}
+				}
+			}
+		})
+	}
+}