Added api/classifications endpoint, requiring a new query

internal/api/classifications_test.go

@@ -0,0 +1,41 @@
+package api
+
+import (
+	"encoding/json"
+	"net/http"
+	"testing"
+
+	"git.avsdev.uk/Go/job-search/internal/types"
+)
+
+// The classifications the opportunities have are listed once each, by code.
+func TestListClassifications(t *testing.T) {
+	url := opportunitiesServer(t, 3)
+
+	var classifications []types.ClassificationCode
+	status := request(t, "GET", url+"/classifications", &classifications)
+	if status != http.StatusOK {
+		t.Fatalf("status %d", status)
+	}
+	if len(classifications) != 2 ||
+		classifications[0].Code != "03000000" ||
+		classifications[1].Code != "72000000" ||
+		classifications[0].ID == 0 {
+		t.Errorf("got %+v; want 03000000 then 72000000, with ids", classifications)
+	}
+}
+
+// With no opportunities, the list is [] in JSON, not null.
+func TestListClassificationsEmpty(t *testing.T) {
+	url := opportunitiesServer(t, 0)
+	res, err := http.Get(url + "/classifications")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	var raw json.RawMessage
+	json.NewDecoder(res.Body).Decode(&raw)
+	if string(raw) != "[]" {
+		t.Errorf("body = %s; want []", raw)
+	}
+}