test: add infra stage parser coverage

infra/package.json

@@ -1,10 +1,13 @@
 {
 	"name": "@cap/infra",
+	"type": "module",
 	"devDependencies": {
-		"sst": "3.17.14"
+		"sst": "3.17.14",
+		"vitest": "~2.1.9"
 	},
 	"scripts": {
-		"sst": "sst"
+		"sst": "sst",
+		"test": "vitest run"
 	},
 	"dependencies": {
 		"@pulumi/github": "^6.7.0",

infra/sst.config.ts

@@ -1,5 +1,7 @@
 /// <reference path="./.sst/platform/config.d.ts" />
 
+import { parseStageName } from "./stage";
+
 const GITHUB_ORG = "CapSoftware";
 const _GITHUB_REPO = "Cap";
 const _GITHUB_APP_ID = "1196731";
@@ -12,16 +14,7 @@ const _CLOUDFLARE_ACCOUNT_ID = "3de2dd633194481d80f68f55257bdbaa";
 const AXIOM_API_TOKEN = "xaat-c0704be6-e942-4935-b068-3b491d7cc00f";
 const AXIOM_DATASET = "cap-otel";
 
-const parsedStage = () => {
-	if ($app.stage === "staging") return { variant: "staging" } as const;
-	if ($app.stage === "production") return { variant: "production" } as const;
-	if ($app.stage.startsWith("git-branch-"))
-		return {
-			variant: "git-branch",
-			branch: $app.stage.slice("git-branch-".length),
-		} as const;
-	throw new Error("Unsupported stage");
-};
+const parsedStage = () => parseStageName($app.stage);
 
 export default $config({
 	app(input) {

infra/stage.test.ts

@@ -0,0 +1,21 @@
+import { describe, expect, it } from "vitest";
+import { parseStageName } from "./stage";
+
+describe("parseStageName", () => {
+	it("recognizes fixed deployment stages", () => {
+		expect(parseStageName("staging")).toEqual({ variant: "staging" });
+		expect(parseStageName("production")).toEqual({ variant: "production" });
+	});
+
+	it("extracts branch names from git branch preview stages", () => {
+		expect(parseStageName("git-branch-add-infra-tests")).toEqual({
+			variant: "git-branch",
+			branch: "add-infra-tests",
+		});
+	});
+
+	it("rejects unsupported stages", () => {
+		expect(() => parseStageName("preview")).toThrow("Unsupported stage");
+		expect(() => parseStageName("git-branch-")).toThrow("Unsupported stage");
+	});
+});

infra/stage.ts

@@ -0,0 +1,15 @@
+export type ParsedStage =
+	| { variant: "staging" }
+	| { variant: "production" }
+	| { variant: "git-branch"; branch: string };
+
+export function parseStageName(stage: string): ParsedStage {
+	if (stage === "staging") return { variant: "staging" };
+	if (stage === "production") return { variant: "production" };
+	if (stage.startsWith("git-branch-")) {
+		const branch = stage.slice("git-branch-".length);
+		if (!branch) throw new Error("Unsupported stage");
+		return { variant: "git-branch", branch };
+	}
+	throw new Error("Unsupported stage");
+}