feat: version 2 beta

tests/adapters/store/add-event.ts

@@ -0,0 +1,220 @@
+import { assertEquals, assertObjectMatch, assertRejects } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import { EventInsertionError, EventValidationError } from "../../../libraries/errors.ts";
+import { makeId } from "../../../libraries/nanoid.ts";
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".addEvent", (getEventStore) => {
+  it("should throw a 'EventValidationError' when providing bad event data", async () => {
+    const { store } = await getEventStore();
+
+    await assertRejects(
+      async () =>
+        store.pushEvent(
+          store.event({
+            type: "user:created",
+            data: {
+              name: {
+                given: "John",
+                familys: "Doe",
+              },
+              email: "john.doe@fixture.none",
+            },
+          } as any),
+        ),
+      EventValidationError,
+    );
+  });
+
+  it("should throw a 'EventInsertionError' on event insertion error", async () => {
+    const { store } = await getEventStore();
+
+    store.events.insert = async () => {
+      throw new Error("Fake Insert Error");
+    };
+
+    await assertRejects(
+      async () =>
+        store.pushEvent(
+          store.event({
+            type: "user:created",
+            data: {
+              name: {
+                given: "John",
+                family: "Doe",
+              },
+              email: "john.doe@fixture.none",
+            },
+            meta: { auditor: "foo" },
+          }),
+        ),
+      EventInsertionError,
+      new EventInsertionError().message,
+    );
+  });
+
+  it("should insert and project 'user:created' event", async () => {
+    const { store, projector } = await getEventStore();
+
+    const stream = makeId();
+    const event = store.event({
+      stream,
+      type: "user:created",
+      data: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john.doe@fixture.none",
+      },
+      meta: { auditor: "foo" },
+    });
+
+    let projectedResult: string = "";
+
+    projector.on("user:created", async (record) => {
+      projectedResult = `${record.data.name?.given} ${record.data.name?.family} | ${record.data.email}`;
+    });
+
+    await store.pushEvent(event);
+
+    assertObjectMatch(await store.events.getByStream(stream).then((rows: any) => rows[0]), event);
+    assertEquals(projectedResult, "John Doe | john.doe@fixture.none");
+  });
+
+  it("should insert 'user:created' and ignore 'project' error", async () => {
+    const { store, projector } = await getEventStore({
+      hooks: {
+        async onError() {
+          // ...
+        },
+      },
+    });
+
+    const stream = makeId();
+    const event = store.event({
+      stream,
+      type: "user:created",
+      data: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john.doe@fixture.none",
+      },
+      meta: {
+        auditor: "admin",
+      },
+    });
+
+    projector.on("user:created", async () => {
+      throw new Error();
+    });
+
+    await store.pushEvent(event);
+
+    assertObjectMatch(await store.events.getByStream(stream).then((rows: any) => rows[0]), event);
+  });
+
+  it("should insert 'user:created' and add it to 'tenant:xyz' relation", async () => {
+    const { store, projector } = await getEventStore();
+
+    const key = `tenant:${makeId()}`;
+
+    projector.on("user:created", async ({ stream }) => {
+      await store.relations.insert(key, stream);
+    });
+
+    await store.pushEvent(
+      store.event({
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "admin",
+        },
+      }),
+    );
+
+    const res1 = await store.getEventsByRelations([key]);
+
+    assertEquals(res1.length, 1);
+
+    await store.pushEvent(
+      store.event({
+        type: "user:created",
+        data: {
+          name: {
+            given: "Jane",
+            family: "Doe",
+          },
+          email: "jane.doe@fixture.none",
+        },
+        meta: {
+          auditor: "admin",
+        },
+      }),
+    );
+
+    const res2 = await store.getEventsByRelations([key]);
+
+    assertEquals(res2.length, 2);
+  });
+
+  it("should insert 'user:email-set' and remove it from 'tenant:xyz' relations", async () => {
+    const { store, projector } = await getEventStore();
+
+    const key = `tenant:${makeId()}`;
+
+    projector.on("user:created", async ({ stream }) => {
+      await store.relations.insert(key, stream);
+    });
+
+    projector.on("user:email-set", async ({ stream }) => {
+      await store.relations.remove(key, stream);
+    });
+
+    await store.pushEvent(
+      store.event({
+        stream: "user-1",
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "admin",
+        },
+      }),
+    );
+
+    const res1 = await store.getEventsByRelations([key]);
+
+    assertEquals(res1.length, 1);
+
+    await store.pushEvent(
+      store.event({
+        stream: "user-1",
+        type: "user:email-set",
+        data: "jane.doe@fixture.none",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    const res2 = await store.getEventsByRelations([key]);
+
+    assertEquals(res2.length, 0);
+  });
+});

tests/adapters/store/add-many-events.ts

@@ -0,0 +1,108 @@
+import { assertEquals, assertObjectMatch, assertRejects } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import { EventValidationError } from "../../../mod.ts";
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".addSequence", (getEventStore) => {
+  it("should insert 'user:created', 'user:name:given-set', and 'user:email-set' in a sequence of events", async () => {
+    const { store } = await getEventStore();
+    const stream = nanoid();
+
+    const events = [
+      store.event({
+        stream,
+        type: "user:created",
+        data: {
+          name: {
+            given: "Jane",
+            family: "Doe",
+          },
+          email: "jane.doe@fixture.none",
+        },
+        meta: {
+          auditor: "admin",
+        },
+      }),
+      store.event({
+        stream,
+        type: "user:name:given-set",
+        data: "John",
+        meta: {
+          auditor: "admin",
+        },
+      }),
+      store.event({
+        stream,
+        type: "user:email-set",
+        data: "john@doe.com",
+        meta: {
+          auditor: "admin",
+        },
+      }),
+    ];
+
+    await store.pushManyEvents(events);
+
+    const records = await store.getEventsByStreams([stream]);
+
+    assertEquals(records.length, 3);
+
+    records.forEach((record, index) => {
+      assertObjectMatch(record, events[index]);
+    });
+
+    const state = await store.reduce({ name: "user", stream, reducer: userReducer });
+
+    assertEquals(state?.name.given, "John");
+    assertEquals(state?.email, "john@doe.com");
+  });
+
+  it("should not commit any events when insert fails", async () => {
+    const { store } = await getEventStore();
+    const stream = nanoid();
+
+    await assertRejects(
+      async () =>
+        store.pushManyEvents([
+          store.event({
+            stream,
+            type: "user:created",
+            data: {
+              name: {
+                given: "Jane",
+                family: "Doe",
+              },
+              email: "jane.doe@fixture.none",
+            },
+            meta: {
+              auditor: "admin",
+            },
+          }),
+          store.event({
+            stream,
+            type: "user:name:given-set",
+            data: {
+              givens: "John",
+            },
+          } as any),
+          store.event({
+            stream,
+            type: "user:email-set",
+            data: "john@doe.com",
+            meta: {
+              auditor: "admin",
+            },
+          }),
+        ]),
+      EventValidationError,
+    );
+
+    const records = await store.getEventsByStreams([stream]);
+
+    assertEquals(records.length, 0);
+  });
+});

tests/adapters/store/create-snapshot.ts

@@ -0,0 +1,91 @@
+import { assertEquals, assertNotEquals, assertObjectMatch } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".createSnapshot", (getEventStore) => {
+  it("should create a new snapshot", async () => {
+    const { store } = await getEventStore();
+    const stream = nanoid();
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:email-set",
+        data: "jane.doe@fixture.none",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:deactivated",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.createSnapshot({ name: "user", stream, reducer: userReducer });
+
+    const snapshot = await store.snapshots.getByStream("user", stream);
+
+    assertNotEquals(snapshot, undefined);
+    assertObjectMatch(snapshot!.state, {
+      name: {
+        given: "John",
+        family: "Doe",
+      },
+      email: "jane.doe@fixture.none",
+      active: false,
+    });
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:activated",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    const events = await store.events.getByStream(stream, { cursor: snapshot!.cursor });
+
+    assertEquals(events.length, 1);
+
+    const state = await store.reduce({ name: "user", stream, reducer: userReducer });
+
+    assertObjectMatch(state!, {
+      name: {
+        given: "John",
+        family: "Doe",
+      },
+      email: "jane.doe@fixture.none",
+      active: true,
+    });
+  });
+});

tests/adapters/store/make-aggregate-reducer.ts

@@ -0,0 +1,25 @@
+import { assertEquals } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".makeAggregateReducer", (getEventStore) => {
+  it("should reduce a user", async () => {
+    const { store } = await getEventStore();
+
+    const userA = await store.aggregate("user").create({ given: "John", family: "Doe" }, "john.doe@fixture.none").setGivenName("Jane").save();
+
+    await userA.snapshot();
+
+    await userA.setFamilyName("Smith").setEmail("jane.smith@fixture.none", "system").save();
+
+    const userB = await store.aggregate("user").getById(userA.id);
+    if (userB === undefined) {
+      throw new Error("Expected user to exist");
+    }
+
+    assertEquals(userB.fullName(), "Jane Smith");
+    assertEquals(userB.email, "jane.smith@fixture.none");
+  });
+});

tests/adapters/store/make-event.ts

@@ -0,0 +1,89 @@
+import { assertEquals, assertLess } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import { RelationPayload } from "../../../types/adapter.ts";
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".makeEvent", (getEventStore) => {
+  it("should make and performantly batch insert a list of events directly", async () => {
+    const { store } = await getEventStore();
+
+    const eventsToInsert = [];
+
+    const t0 = performance.now();
+
+    let count = 10_000;
+    while (count--) {
+      eventsToInsert.push(
+        store.event({
+          type: "user:created",
+          data: {
+            name: {
+              given: "John",
+              family: "Doe",
+            },
+            email: "john.doe@fixture.none",
+          },
+          meta: {
+            auditor: "system",
+          },
+        }),
+      );
+    }
+
+    const t1 = performance.now();
+
+    assertLess((t1 - t0) / 1000, 5);
+
+    const t3 = performance.now();
+
+    await store.events.insertMany(eventsToInsert);
+
+    const t4 = performance.now();
+
+    assertLess((t4 - t3) / 1000, 5);
+
+    const events = await store.getEvents();
+
+    assertEquals(events.length, 10_000);
+  });
+
+  it("should performantly create and remove event relations", async () => {
+    const { store } = await getEventStore();
+
+    const relations: RelationPayload[] = [];
+
+    let count = 10_000;
+    while (count--) {
+      const event = store.event({
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "system",
+        },
+      });
+      relations.push({ key: `test:xyz`, stream: event.stream });
+    }
+
+    const t0 = performance.now();
+    await store.relations.insertMany(relations);
+    const tr0 = (performance.now() - t0) / 1000;
+
+    assertEquals((await store.relations.getByKey(`test:xyz`)).length, 10_000);
+    assertLess(tr0, 5);
+
+    const t1 = performance.now();
+    await store.relations.removeMany(relations);
+    const tr1 = (performance.now() - t1) / 1000;
+
+    assertEquals((await store.relations.getByKey(`test:xyz`)).length, 0);
+    assertLess(tr1, 10);
+  });
+});

tests/adapters/store/make-reducer.ts

@@ -0,0 +1,120 @@
+import { assertEquals } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import { makeId } from "../../../libraries/nanoid.ts";
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userPostReducer } from "../mocks/user-posts-reducer.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".makeReducer", (getEventStore) => {
+  it("should create a 'user' reducer and only reduce filtered events", async () => {
+    const { store } = await getEventStore();
+
+    const streamA = nanoid();
+    const streamB = nanoid();
+
+    await store.pushEvent(
+      store.event({
+        stream: streamA,
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "system",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream: streamB,
+        type: "user:created",
+        data: {
+          name: {
+            given: "Peter",
+            family: "Parker",
+          },
+          email: "peter.parker@fixture.none",
+        },
+        meta: {
+          auditor: "system",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream: streamA,
+        type: "user:name:given-set",
+        data: "Jane",
+        meta: {
+          auditor: "system",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream: streamA,
+        type: "user:email-set",
+        data: "jane.doe@fixture.none",
+        meta: {
+          auditor: "system",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream: streamB,
+        type: "user:email-set",
+        data: "spiderman@fixture.none",
+        meta: {
+          auditor: "system",
+        },
+      }),
+    );
+
+    const state = await store.reduce({ name: "user", stream: streamA, reducer: userReducer, filter: { types: ["user:created", "user:email-set"] } });
+
+    assertEquals(state?.name, { given: "John", family: "Doe" });
+    assertEquals(state?.email, "jane.doe@fixture.none");
+  });
+
+  it("should create a 'post:count' reducer and retrieve post correct post count", async () => {
+    const { store, projector } = await getEventStore();
+    const auditor = nanoid();
+
+    projector.on("post:created", async ({ stream, meta: { auditor } }) => {
+      await store.relations.insert(`user:${auditor}:posts`, stream);
+    });
+
+    const post1 = makeId();
+    const post2 = makeId();
+    const post3 = makeId();
+
+    await store.pushEvent(store.event({ stream: post1, type: "post:created", data: { title: "Post #1", body: "Sample #1" }, meta: { auditor } }));
+    await store.pushEvent(store.event({ stream: post2, type: "post:created", data: { title: "Post #2", body: "Sample #2" }, meta: { auditor } }));
+    await store.pushEvent(store.event({ stream: post2, type: "post:removed", meta: { auditor } }));
+    await store.pushEvent(store.event({ stream: post3, type: "post:created", data: { title: "Post #3", body: "Sample #3" }, meta: { auditor } }));
+
+    const events = await store.getEventsByRelations([`user:${auditor}:posts`]);
+
+    assertEquals(events.length, 4);
+
+    const state = await store.reduce({ name: "user", relation: `user:${auditor}:posts`, reducer: userPostReducer });
+
+    assertEquals(state?.posts, [
+      { id: post1, author: auditor },
+      { id: post3, author: auditor },
+    ]);
+    assertEquals(state?.count, 2);
+  });
+});

tests/adapters/store/once-projection.ts

@@ -0,0 +1,94 @@
+import { assertEquals, assertObjectMatch } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import { makeId } from "../../../libraries/nanoid.ts";
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>("projector.once", (getEventStore) => {
+  it("should handle successfull projection", async () => {
+    const { store, projector } = await getEventStore();
+
+    const stream = makeId();
+    const event = store.event({
+      stream,
+      type: "user:created",
+      data: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john.doe@fixture.none",
+      },
+      meta: {
+        auditor: "foo",
+      },
+    });
+
+    let emailId: string | Error | undefined;
+
+    projector.once(
+      "user:created",
+      async () => {
+        return { id: "fake-email-id" };
+      },
+      {
+        async onError({ error }) {
+          emailId = error as Error;
+        },
+        async onSuccess({ data }) {
+          emailId = data.id;
+        },
+      },
+    );
+
+    await store.pushEvent(event);
+
+    assertObjectMatch(await store.events.getByStream(stream).then((rows: any) => rows[0]), event);
+    assertEquals(emailId, "fake-email-id");
+  });
+
+  it("should handle failed projection", async () => {
+    const { store, projector } = await getEventStore();
+
+    const stream = makeId();
+    const event = store.event({
+      stream,
+      type: "user:created",
+      data: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john.doe@fixture.none",
+      },
+      meta: {
+        auditor: "foo",
+      },
+    });
+
+    let emailId: string | undefined;
+
+    projector.once(
+      "user:created",
+      async () => {
+        fakeEmail();
+      },
+      {
+        async onError({ error }) {
+          emailId = (error as Error).message;
+        },
+        async onSuccess() {},
+      },
+    );
+
+    await store.pushEvent(event);
+
+    assertObjectMatch(await store.events.getByStream(stream).then((rows: any) => rows[0]), event);
+    assertEquals(emailId, "Failed to send email!");
+  });
+});
+
+function fakeEmail() {
+  throw new Error("Failed to send email!");
+}

tests/adapters/store/providers/relations.ts

@@ -0,0 +1,34 @@
+import { assertEquals } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import type { EventStoreFactory } from "../../mocks/events.ts";
+import { describe } from "../../utilities/describe.ts";
+
+export default describe<EventStoreFactory>("relations", (getEventStore) => {
+  it("should create a new relation", async () => {
+    const { store } = await getEventStore();
+
+    const key = "sample";
+    const stream = nanoid();
+
+    await store.relations.insert(key, stream);
+
+    assertEquals(await store.relations.getByKey(key), [stream]);
+  });
+
+  it("should ignore duplicate relations", async () => {
+    const { store } = await getEventStore();
+
+    const key = "sample";
+    const stream = nanoid();
+
+    await store.relations.insertMany([
+      { key, stream },
+      { key, stream },
+    ]);
+    await store.relations.insert(key, stream);
+
+    assertEquals(await store.relations.getByKey(key), [stream]);
+  });
+});

tests/adapters/store/push-aggregate.ts

@@ -0,0 +1,42 @@
+import { assertEquals, assertObjectMatch } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".pushAggregate", (getEventStore) => {
+  it("should successfully commit pending aggregate events to the event store", async () => {
+    const { store } = await getEventStore();
+
+    const user = store
+      .aggregate("user")
+      .create({ given: "Jane", family: "Doe" }, "jane.doe@fixture.none")
+      .setGivenName("John")
+      .setEmail("john.doe@fixture.none", "admin");
+
+    assertEquals(user.toPending().length, 3);
+
+    await store.pushAggregate(user);
+
+    assertEquals(user.toPending().length, 0);
+
+    const records = await store.getEventsByStreams([user.id]);
+
+    assertEquals(records.length, 3);
+
+    assertObjectMatch(records[0], { stream: user.id, data: { name: { given: "Jane", family: "Doe" }, email: "jane.doe@fixture.none" } });
+    assertObjectMatch(records[1], { stream: user.id, data: "John" });
+    assertObjectMatch(records[2], { stream: user.id, data: "john.doe@fixture.none", meta: { auditor: "admin" } });
+
+    const state = await store.reduce({ name: "user", stream: user.id, reducer: userReducer });
+
+    assertObjectMatch(state!, {
+      name: {
+        given: "John",
+        family: "Doe",
+      },
+      email: "john.doe@fixture.none",
+    });
+  });
+});

tests/adapters/store/push-many-aggregates.ts

@@ -0,0 +1,62 @@
+import { assertEquals, assertObjectMatch } from "@std/assert";
+import { it } from "@std/testing/bdd";
+
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".pushManyAggregates", (getEventStore) => {
+  it("should successfully commit pending aggregates events to the event store", async () => {
+    const { store } = await getEventStore();
+
+    const userA = store
+      .aggregate("user")
+      .create({ given: "Jane", family: "Doe" }, "jane.doe@fixture.none")
+      .setGivenName("John")
+      .setEmail("john.doe@fixture.none", "admin");
+
+    const userB = store
+      .aggregate("user")
+      .create({ given: "Peter", family: "Doe" }, "peter.doe@fixture.none")
+      .setGivenName("Barry")
+      .setEmail("barry.doe@fixture.none", "admin");
+
+    assertEquals(userA.toPending().length, 3);
+    assertEquals(userB.toPending().length, 3);
+
+    await store.pushManyAggregates([userA, userB]);
+
+    assertEquals(userA.toPending().length, 0);
+    assertEquals(userB.toPending().length, 0);
+
+    const records = await store.getEventsByStreams([userA.id, userB.id]);
+
+    assertEquals(records.length, 6);
+
+    assertObjectMatch(records[0], { stream: userA.id, data: { name: { given: "Jane", family: "Doe" }, email: "jane.doe@fixture.none" } });
+    assertObjectMatch(records[1], { stream: userA.id, data: "John" });
+    assertObjectMatch(records[2], { stream: userA.id, data: "john.doe@fixture.none", meta: { auditor: "admin" } });
+    assertObjectMatch(records[3], { stream: userB.id, data: { name: { given: "Peter", family: "Doe" }, email: "peter.doe@fixture.none" } });
+    assertObjectMatch(records[4], { stream: userB.id, data: "Barry" });
+    assertObjectMatch(records[5], { stream: userB.id, data: "barry.doe@fixture.none", meta: { auditor: "admin" } });
+
+    const stateA = await store.reduce({ name: "user", stream: userA.id, reducer: userReducer });
+    const stateB = await store.reduce({ name: "user", stream: userB.id, reducer: userReducer });
+
+    assertObjectMatch(stateA!, {
+      name: {
+        given: "John",
+        family: "Doe",
+      },
+      email: "john.doe@fixture.none",
+    });
+
+    assertObjectMatch(stateB!, {
+      name: {
+        given: "Barry",
+        family: "Doe",
+      },
+      email: "barry.doe@fixture.none",
+    });
+  });
+});

tests/adapters/store/reduce.ts

@@ -0,0 +1,103 @@
+import { assertEquals } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import type { EventStoreFactory } from "../mocks/events.ts";
+import { userReducer } from "../mocks/user-reducer.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".reduce", (getEventStore) => {
+  it("should return reduced state", async () => {
+    const { store } = await getEventStore();
+    const stream = nanoid();
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:email-set",
+        data: "jane.doe@fixture.none",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    const state = await store.reduce({ name: "user", stream, reducer: userReducer });
+
+    assertEquals(state, {
+      name: { given: "John", family: "Doe" },
+      email: "jane.doe@fixture.none",
+      active: true,
+      posts: { list: [], count: 0 },
+    });
+  });
+
+  it("should return snapshot if it exists and no new events were found", async () => {
+    const { store } = await getEventStore();
+    const stream = nanoid();
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:created",
+        data: {
+          name: {
+            given: "John",
+            family: "Doe",
+          },
+          email: "john.doe@fixture.none",
+        },
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.pushEvent(
+      store.event({
+        stream,
+        type: "user:email-set",
+        data: "jane.doe@fixture.none",
+        meta: {
+          auditor: "super",
+        },
+      }),
+    );
+
+    await store.createSnapshot({ name: "user", stream, reducer: userReducer });
+
+    const state = await store.reduce({ name: "user", stream, reducer: userReducer });
+
+    assertEquals(state, {
+      name: { given: "John", family: "Doe" },
+      email: "jane.doe@fixture.none",
+      active: true,
+      posts: { list: [], count: 0 },
+    });
+  });
+
+  it("should return undefined if stream does not have events", async () => {
+    const stream = nanoid();
+    const { store } = await getEventStore();
+    const state = await store.reduce({ name: "user", stream, reducer: userReducer });
+
+    assertEquals(state, undefined);
+  });
+});

tests/adapters/store/replay-events.ts

@@ -0,0 +1,94 @@
+import { assertObjectMatch } from "@std/assert";
+import { it } from "@std/testing/bdd";
+import { nanoid } from "nanoid";
+
+import { EventStoreFactory } from "../mocks/events.ts";
+import { describe } from "../utilities/describe.ts";
+
+export default describe<EventStoreFactory>(".replayEvents", (getEventStore) => {
+  it("should replay events", async () => {
+    const { store, projector } = await getEventStore();
+    const stream = nanoid();
+
+    const record: Record<string, any> = {};
+
+    projector.on("user:created", async ({ stream, data: { name, email } }) => {
+      record[stream] = {
+        name,
+        email,
+      };
+    });
+
+    projector.on("user:name:given-set", async ({ stream, data }) => {
+      record[stream].name.given = data;
+    });
+
+    projector.on("user:email-set", async ({ stream, data }) => {
+      record[stream].email = data;
+    });
+
+    await store.pushManyEvents([
+      store.event({
+        stream,
+        type: "user:created",
+        data: {
+          name: {
+            given: "Jane",
+            family: "Doe",
+          },
+          email: "jane.doe@fixture.none",
+        },
+        meta: {
+          auditor: "admin",
+        },
+      }),
+      store.event({
+        stream,
+        type: "user:name:given-set",
+        data: "John",
+        meta: {
+          auditor: "admin",
+        },
+      }),
+      store.event({
+        stream,
+        type: "user:email-set",
+        data: "john@doe.com",
+        meta: {
+          auditor: "admin",
+        },
+      }),
+    ]);
+
+    assertObjectMatch(record, {
+      [stream]: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john@doe.com",
+      },
+    });
+
+    delete record[stream];
+
+    const promises = [];
+
+    const records = await store.getEventsByStreams([stream]);
+    for (const record of records) {
+      promises.push(projector.push(record, { hydrated: true, outdated: false }));
+    }
+
+    await Promise.all(promises);
+
+    assertObjectMatch(record, {
+      [stream]: {
+        name: {
+          given: "John",
+          family: "Doe",
+        },
+        email: "john@doe.com",
+      },
+    });
+  });
+});