test: define large-library browse strategy contract

test/server/utils/libraryBrowseCount.test.js

@@ -0,0 +1,29 @@
+const chai = require('chai')
+const expect = chai.expect
+
+const { loadBrowseCount } = require('../../../server/utils/queries/libraryBrowseCount')
+
+describe('libraryBrowseCount', () => {
+  it('returns deferred exact count metadata on first chunk', async () => {
+    const payload = await loadBrowseCount({
+      mode: 'deferred-exact',
+      exactCountLoader: async () => 123
+    })
+
+    expect(payload).to.deep.equal({ total: 123, isExact: true, isDeferred: true })
+  })
+
+  it('skips exact count work on follow-up endless-scroll chunks', async () => {
+    let called = false
+    const payload = await loadBrowseCount({
+      mode: 'skip',
+      exactCountLoader: async () => {
+        called = true
+        return 123
+      }
+    })
+
+    expect(payload).to.deep.equal({ total: null, isExact: false, isDeferred: true })
+    expect(called).to.equal(false)
+  })
+})