test(#792): cover roster guard and installer heading

packages/mosaic/src/commands/fleet.spec.ts

@@ -60,6 +60,7 @@ import {
   type SleepFn,
 } from './fleet.js';
 import { registerAgentCommand } from './agent.js';
+import { parseFleetRosterDocument, readFleetRosterText } from '../fleet/fleet-roster-v1.js';
 
 function buildProgram(): Command {
   const program = new Command();
@@ -166,6 +167,55 @@ describe('registerFleetCommand', () => {
   });
 });
 
+describe('fleet roster configuration failures', () => {
+  it('reports a missing roster with an actionable initialization hint', async () => {
+    const home = await tempDir();
+    try {
+      const program = buildProgram();
+
+      await expect(
+        program.parseAsync(['node', 'mosaic', 'fleet', '--mosaic-home', home, 'ps']),
+      ).rejects.toThrow(
+        `No fleet roster found at ${join(home, 'fleet', 'roster.json')}. Run \`mosaic fleet init\``,
+      );
+    } finally {
+      await rm(home, { recursive: true, force: true });
+    }
+  });
+
+  it('reports a malformed roster with the path and repair hint', async () => {
+    const home = await tempDir();
+    const rosterPath = join(home, 'fleet', 'roster.json');
+    try {
+      await mkdir(dirname(rosterPath), { recursive: true });
+      await writeFile(rosterPath, '{not valid json');
+
+      await expect(loadFleetRoster(rosterPath)).rejects.toThrow(
+        `Fleet roster at ${rosterPath} is invalid. Fix the file or run \`mosaic fleet init --force\``,
+      );
+    } finally {
+      await rm(home, { recursive: true, force: true });
+    }
+  });
+
+  it('reports an unreadable roster without exposing the filesystem error', async () => {
+    const home = await tempDir();
+    try {
+      await expect(readFleetRosterText(home)).rejects.toThrow(
+        `Could not read fleet roster at ${home}. Check the file exists and is readable.`,
+      );
+    } finally {
+      await rm(home, { recursive: true, force: true });
+    }
+  });
+
+  it('reports a malformed roster while selecting the v1/v2 command path', () => {
+    expect(() => parseFleetRosterDocument('version: [', '/srv/mosaic/fleet/roster.yaml')).toThrow(
+      'Fleet roster at /srv/mosaic/fleet/roster.yaml is invalid. Fix the file or run `mosaic fleet init --force`.',
+    );
+  });
+});
+
 describe('fleet roster parsing', () => {
   let cleanup: string | undefined;