diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 94f7073..9a22db1 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -32,3 +32,28 @@ jobs:
         run: |
           go vet ./...
           staticcheck ./...
+
+  test:
+    strategy:
+      matrix:
+        go: ['1.20', '1.21', '1.22']
+    name: test @ Go ${{ matrix.go }}
+    runs-on: ubuntu-latest
+    steps:
+    - name: Install Go
+      uses: actions/setup-go@v3
+      with:
+        go-version: ${{ matrix.go }}
+
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - uses: actions/cache@v3
+      with:
+        path: ~/go/pkg/mod
+        key: ${{ runner.os }}-build-${{ hashFiles('**/go.sum') }}
+        restore-keys: |
+          ${{ runner.os }}-build-
+
+    - name: Test
+      run: go test -v -race ./...
diff --git a/go.mod b/go.mod
index b604059..14da4a9 100644
--- a/go.mod
+++ b/go.mod
@@ -10,6 +10,7 @@ require (
 )
 
 require (
+	github.com/DATA-DOG/go-sqlmock v1.5.2 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-isatty v0.0.19 // indirect
 	golang.org/x/sys v0.12.0 // indirect
diff --git a/go.sum b/go.sum
index 7a36ec3..4ad3ca8 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/DATA-DOG/go-sqlmock v1.5.2 h1:OcvFkGmslmlZibjAjaHm3L//6LiuBgolP7OputlJIzU=
+github.com/DATA-DOG/go-sqlmock v1.5.2/go.mod h1:88MAG/4G7SMwSE3CeA0ZKzrT5CiOU3OJ+JlNzwDqpNU=
 github.com/coreos/go-systemd/v22 v22.5.0/go.mod h1:Y58oyj3AT4RCenI/lSvhwexgC+NSVTIJ3seZv2GcEnc=
 github.com/go-sql-driver/mysql v1.6.0/go.mod h1:DCzpHaOWr8IXmIStZouvnhqoel9Qv2LBy8hT2VhHyBg=
 github.com/go-sql-driver/mysql v1.7.1 h1:lUIinVbN1DY0xBg0eMOzmmtGoHwWBbvnWubQUrtU8EI=
@@ -5,6 +7,7 @@ github.com/go-sql-driver/mysql v1.7.1/go.mod h1:OXbVy3sEdcQ2Doequ6Z5BW6fXNQTmx+9
 github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
 github.com/jmoiron/sqlx v1.3.5 h1:vFFPA71p1o5gAeqtEAwLU4dnX2napprKtHr7PYIcN3g=
 github.com/jmoiron/sqlx v1.3.5/go.mod h1:nRVWtLre0KfCLJvgxzCsLVMogSvQ1zNJtpYr2Ccp0mQ=
+github.com/kisielk/sqlstruct v0.0.0-20201105191214-5f3e10d3ab46/go.mod h1:yyMNCyc/Ib3bDTKd379tNMpB/7/H5TjM2Y9QJ5THLbE=
 github.com/lib/pq v1.2.0 h1:LXpIM/LZ5xGFhOpXAQUIMM1HdyqzVYM13zNdjCEEcA0=
 github.com/lib/pq v1.2.0/go.mod h1:5WUZQaWbwv1U+lTReE5YruASi9Al49XbQIvNi/34Woo=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
diff --git a/nanoq_test.go b/nanoq_test.go
new file mode 100644
index 0000000..a0e29e5
--- /dev/null
+++ b/nanoq_test.go
@@ -0,0 +1,186 @@
+package nanoq_test
+
+import (
+	"context"
+	"errors"
+	"slices"
+	"testing"
+	"time"
+
+	"github.com/DATA-DOG/go-sqlmock"
+	"github.com/bojanz/nanoq"
+	"github.com/go-sql-driver/mysql"
+	"github.com/jmoiron/sqlx"
+	"github.com/oklog/ulid/v2"
+	"github.com/rs/zerolog"
+)
+
+func Test_NewTask(t *testing.T) {
+	t.Run("empty_task", func(t *testing.T) {
+		task := nanoq.NewTask("my-type", nil)
+
+		if _, err := ulid.ParseStrict(task.ID); err != nil {
+			t.Errorf("id: %v", err)
+		}
+		if task.Type != "my-type" {
+			t.Errorf("type: got %q, want %q", task.Type, "my-type")
+		}
+		if !slices.Equal(task.Payload, []byte("{}")) {
+			t.Errorf("payload: got %q, want %q", task.Payload, []byte("{}"))
+		}
+		if task.MaxRetries != 10 {
+			t.Errorf("max retries: got %v, want %v", task.MaxRetries, 10)
+		}
+		if task.CreatedAt.IsZero() {
+			t.Errorf("created_at must not be empty")
+		}
+		if task.ScheduledAt.IsZero() {
+			t.Errorf("scheduled_at must not be empty")
+		}
+		if !task.CreatedAt.Equal(task.ScheduledAt) {
+			t.Errorf("created_at %q does not match scheduled_at %q", task.CreatedAt, task.ScheduledAt)
+		}
+		if task.Fingerprint != "25c084d0" {
+			t.Errorf("fingerprint: got %q, want %q", task.Fingerprint, "25c084d0")
+		}
+	})
+
+	t.Run("payload_and_options", func(t *testing.T) {
+		payload := []byte(`{"product_id": "123", "user_id": "456"}`)
+		scheduledAt := time.Date(2030, 1, 1, 0, 0, 0, 0, time.UTC)
+		task := nanoq.NewTask("my-type", payload, nanoq.WithMaxRetries(2), nanoq.WithScheduledAt(scheduledAt))
+
+		if _, err := ulid.ParseStrict(task.ID); err != nil {
+			t.Errorf("id: %v", err)
+		}
+		if task.Type != "my-type" {
+			t.Errorf("type: got %q, want %q", task.Type, "my-type")
+		}
+		if !slices.Equal(task.Payload, payload) {
+			t.Errorf("payload: got %q, want %q", task.Payload, payload)
+		}
+		if task.MaxRetries != 2 {
+			t.Errorf("max retries: got %v, want %v", task.MaxRetries, 2)
+		}
+		if task.CreatedAt.IsZero() {
+			t.Errorf("created_at must not be empty")
+		}
+		if !task.ScheduledAt.Equal(scheduledAt) {
+			t.Errorf("created_at: got %q want %q", task.ScheduledAt, scheduledAt)
+		}
+		if task.Fingerprint != "3f16b1c4" {
+			t.Errorf("fingerprint: got %q, want %q", task.Fingerprint, "3f16b1c4")
+		}
+	})
+
+	t.Run("custom_fingerprint", func(t *testing.T) {
+		payload := []byte(`{"product_id": "123", "user_id": "456"}`)
+		fingerprintData := []byte(`{"product_id": "123"}`)
+		task := nanoq.NewTask("my-type", payload, nanoq.WithFingerprintData(fingerprintData))
+
+		if task.Type != "my-type" {
+			t.Errorf("type: got %q, want %q", task.Type, "my-type")
+		}
+		if !slices.Equal(task.Payload, payload) {
+			t.Errorf("payload: got %q, want %q", task.Payload, payload)
+		}
+		if task.Fingerprint != "a48cb4c4" {
+			t.Errorf("fingerprint: got %q, want %q", task.Fingerprint, "a48cb4c4")
+		}
+	})
+}
+
+func TestClient_CreateTask(t *testing.T) {
+	ctx := context.Background()
+	db, mock, _ := sqlmock.New()
+	defer db.Close()
+	client := nanoq.NewClient(sqlx.NewDb(db, "sqlmock"))
+	task := nanoq.NewTask("my-type", nil)
+
+	t.Run("success", func(t *testing.T) {
+		mock.ExpectBegin()
+		mock.ExpectExec(`INSERT INTO tasks(.+) VALUES(.+)`).
+			WithArgs(task.ID, task.Fingerprint, task.Type, task.Payload, task.Retries, task.MaxRetries, task.CreatedAt, task.ScheduledAt).
+			WillReturnResult(sqlmock.NewResult(0, 1))
+		mock.ExpectCommit()
+
+		client.RunTransaction(ctx, func(tx *sqlx.Tx) error {
+			return client.CreateTask(ctx, tx, task)
+		})
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Error(err)
+		}
+	})
+
+	t.Run("duplicate", func(t *testing.T) {
+		mock.ExpectBegin()
+		mock.ExpectExec(`INSERT INTO tasks(.+) VALUES(.+)`).
+			WithArgs(task.ID, task.Fingerprint, task.Type, task.Payload, task.Retries, task.MaxRetries, task.CreatedAt, task.ScheduledAt).
+			WillReturnError(&mysql.MySQLError{Number: 1022})
+		mock.ExpectRollback()
+
+		err := client.RunTransaction(ctx, func(tx *sqlx.Tx) error {
+			return client.CreateTask(ctx, tx, task)
+		})
+		if err != nanoq.ErrDuplicateTask {
+			t.Errorf("got %v, want ErrDuplicateTask", err)
+		}
+
+		if err := mock.ExpectationsWereMet(); err != nil {
+			t.Error(err)
+		}
+	})
+}
+
+func TestProcessor_Run(t *testing.T) {
+	db, mock, _ := sqlmock.New()
+	defer db.Close()
+	client := nanoq.NewClient(sqlx.NewDb(db, "sqlmock"))
+	processor := nanoq.NewProcessor(client, zerolog.Nop())
+	processor.Handle("my-type", func(ctx context.Context, task nanoq.Task) error {
+		// Fail the task once.
+		if task.Retries == 0 {
+			return errors.New("temporary error")
+		}
+		return nil
+	})
+	errorHandlerCalled := 0
+	processor.OnError(func(ctx context.Context, task nanoq.Task, err error) {
+		errorHandlerCalled++
+	})
+
+	// First task claim and retry.
+	mock.ExpectBegin()
+	rows := sqlmock.NewRows([]string{"id", "fingerprint", "type", "payload", "retries", "max_retries", "created_at", "scheduled_at"}).
+		AddRow("01HQJHTZCAT5WDCGVTWJ640VMM", "25c084d0", "my-type", "{}", "0", "1", time.Now(), time.Now())
+	mock.ExpectQuery(`SELECT \* FROM tasks WHERE(.+)`).WillReturnRows(rows)
+
+	mock.ExpectExec("UPDATE tasks SET retries = (.+), scheduled_at = (.+) WHERE id = (.+)").WithArgs(1, sqlmock.AnyArg(), "01HQJHTZCAT5WDCGVTWJ640VMM").
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectCommit()
+
+	// Second task claim and deletion (due to success).
+	mock.ExpectBegin()
+	rows = sqlmock.NewRows([]string{"id", "fingerprint", "type", "payload", "retries", "max_retries", "created_at", "scheduled_at"}).
+		AddRow("01HQJHTZCAT5WDCGVTWJ640VMM", "25c084d0", "my-type", "{}", "1", "1", time.Now(), time.Now())
+	mock.ExpectQuery(`SELECT \* FROM tasks WHERE(.+)`).WillReturnRows(rows)
+
+	mock.ExpectExec("DELETE FROM tasks WHERE id = (.+)").WithArgs("01HQJHTZCAT5WDCGVTWJ640VMM").
+		WillReturnResult(sqlmock.NewResult(0, 1))
+	mock.ExpectCommit()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go processor.Run(ctx, 1, 1*time.Second)
+	time.Sleep(1 * time.Second)
+	cancel()
+
+	err := mock.ExpectationsWereMet()
+	if err != nil {
+		t.Error(err)
+	}
+
+	if errorHandlerCalled != 1 {
+		t.Errorf("erorr handler called %v times instead of %v", errorHandlerCalled, 1)
+	}
+}