Split main into fetch and render, add tests

TODO.md

@@ -34,7 +34,7 @@
 
 ## Tests / CI
 
-- [ ] Split into `fetch(url)` and `render(w io.Writer, summary)`; test `render`
+- [x] Split into `fetch(url)` and `render(w io.Writer, summary)`; test `render`
       with a JSON fixture and `fetch` with `httptest.NewServer`
 - [ ] Add a lint job (`golangci/golangci-lint-action`) to CI
 - [x] CI targets Go `oldstable` and `stable` (via `actions/setup-go` aliases)

github_status.go

@@ -7,6 +7,7 @@ package main
 import (
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"os"
 	"time"
@@ -44,33 +45,52 @@ type summary struct {
 	} `json:"status"`
 }
 
+const summaryURL = "https://kctbh9vrtdwd.statuspage.io/api/v2/summary.json"
+
 func main() {
-	client := &http.Client{Timeout: 10 * time.Second}
-	response, err := client.Get("https://kctbh9vrtdwd.statuspage.io/api/v2/summary.json")
+	s, err := fetch(summaryURL)
 	checkErr(err)
+	checkErr(render(os.Stdout, s))
+}
+
+// fetch retrieves and decodes the status page summary at url.
+func fetch(url string) (summary, error) {
+	var s summary
+
+	client := &http.Client{Timeout: 10 * time.Second}
+	response, err := client.Get(url)
+	if err != nil {
+		return s, err
+	}
 	defer func() { _ = response.Body.Close() }()
 
 	if response.StatusCode != http.StatusOK {
-		checkErr(fmt.Errorf("unexpected HTTP status: %s", response.Status))
+		return s, fmt.Errorf("unexpected HTTP status: %s", response.Status)
 	}
 
-	var responseObject summary
-	err = json.NewDecoder(response.Body).Decode(&responseObject)
-	checkErr(err)
+	if err := json.NewDecoder(response.Body).Decode(&s); err != nil {
+		return s, fmt.Errorf("decoding summary: %w", err)
+	}
+	return s, nil
+}
 
-	for _, component := range responseObject.Components {
-		fmt.Printf("%-60s", component.Name)
+// render writes one line per component to w, with the status colorized.
+func render(w io.Writer, s summary) error {
+	for _, component := range s.Components {
+		c := color.New(color.FgYellow)
 		if component.Status == "operational" {
-			color.Set(color.FgGreen)
+			c = color.New(color.FgGreen)
 		} else if component.Status == "major_outage" {
-			color.Set(color.FgRed)
-		} else {
-			color.Set(color.FgYellow)
+			c = color.New(color.FgRed)
+		}
+		if _, err := fmt.Fprintf(w, "%-60s", component.Name); err != nil {
+			return err
+		}
+		if _, err := c.Fprintln(w, component.Status); err != nil {
+			return err
 		}
-		fmt.Printf("%s\n", component.Status)
-		color.Unset()
 	}
-
+	return nil
 }
 
 func checkErr(err error) {

github_status_test.go

@@ -0,0 +1,100 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/fatih/color"
+)
+
+func TestMain(m *testing.M) {
+	color.NoColor = true
+	os.Exit(m.Run())
+}
+
+func serveFixture(t *testing.T) *httptest.Server {
+	t.Helper()
+	data, err := os.ReadFile("testdata/summary.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write(data)
+	}))
+	t.Cleanup(srv.Close)
+	return srv
+}
+
+func TestFetch(t *testing.T) {
+	srv := serveFixture(t)
+
+	s, err := fetch(srv.URL)
+	if err != nil {
+		t.Fatalf("fetch: %v", err)
+	}
+	if got := len(s.Components); got != 3 {
+		t.Fatalf("got %d components, want 3", got)
+	}
+	if got := s.Status.Description; got != "Partial System Outage" {
+		t.Errorf("status description = %q", got)
+	}
+}
+
+func TestFetchErrors(t *testing.T) {
+	tests := []struct {
+		name    string
+		handler http.HandlerFunc
+		want    string
+	}{
+		{
+			name: "server error",
+			handler: func(w http.ResponseWriter, _ *http.Request) {
+				w.WriteHeader(http.StatusInternalServerError)
+			},
+			want: "unexpected HTTP status: 500",
+		},
+		{
+			name: "malformed JSON",
+			handler: func(w http.ResponseWriter, _ *http.Request) {
+				_, _ = fmt.Fprint(w, "<html>not json</html>")
+			},
+			want: "decoding summary",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			srv := httptest.NewServer(tt.handler)
+			defer srv.Close()
+
+			_, err := fetch(srv.URL)
+			if err == nil || !strings.Contains(err.Error(), tt.want) {
+				t.Fatalf("got error %v, want one containing %q", err, tt.want)
+			}
+		})
+	}
+}
+
+func TestRender(t *testing.T) {
+	s, err := fetch(serveFixture(t).URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var buf bytes.Buffer
+	if err := render(&buf, s); err != nil {
+		t.Fatal(err)
+	}
+
+	want := fmt.Sprintf("%-60s%s\n%-60s%s\n%-60s%s\n",
+		"Git Operations", "operational",
+		"Actions", "major_outage",
+		"Pages", "degraded_performance")
+	if got := buf.String(); got != want {
+		t.Errorf("render output mismatch\ngot:\n%s\nwant:\n%s", got, want)
+	}
+}

testdata/summary.json

@@ -0,0 +1,17 @@
+{
+  "page": {
+    "id": "kctbh9vrtdwd",
+    "name": "GitHub",
+    "url": "https://www.githubstatus.com",
+    "time_zone": "Etc/UTC",
+    "updated_at": "2026-11-14T12:00:00.000Z"
+  },
+  "components": [
+    {"id": "1", "name": "Git Operations", "status": "operational", "group": false, "position": 1},
+    {"id": "2", "name": "Actions", "status": "major_outage", "group": false, "position": 2},
+    {"id": "3", "name": "Pages", "status": "degraded_performance", "group": false, "position": 3}
+  ],
+  "incidents": [],
+  "scheduled_maintenances": [],
+  "status": {"indicator": "major", "description": "Partial System Outage"}
+}