what will be a better approach to StreamData when one has 2 maps? - unit-testing

Question

The following property test is working fine, however, I think there should be a better and more efficient way of implementing this.
params in the following property will be something like this:
%{
"project_id" => "%&!XX!hLCfsS-dO_<fy?kpi4y=AEumQ$Xn:#.7Fl TnH~k>ZLB[q",
"task_id" => [
%{"asset_id" => 10, "tasks" => []},
%{"asset_id" => 10, "tasks" => []}
]
}
Property Testing:
property "bad project value" do
[user, project] = prepare()
user_gen = constant(%{id: user.id})
project_gen = constant("project_id")
|> map_of(Factory.my_terms, length: 1)
tasks = constant(%{"asset_id" => 10, "tasks" => []})
|> list_of(length: 2)
tasks_gen = constant("task_id")
|> map_of(tasks, length: 1)
check all project <- project_gen, task <- tasks_gen , user <- user_gen do
params = Map.merge(project, task)
res = ProjectTask.Save.save(params, user)
assert res == {:error, :not_found}
end
Factory.my_terms is the following:
def my_terms() do
one_of([string(:alphanumeric), string(:ascii), atom(:alphanumeric), integer(), binary()])
end
UPDATE
property "bad project value" do
[user, project] = prepare()
project_gen = constant("project_id")
|> map_of(Factory.my_terms, length: 1)
tasks = List.duplicate(%{"asset_id" => 10, "tasks" => []}, 2)
tasks = %{"tasks" => tasks}
check all project <- project_gen do
params = Map.merge(project, tasks)
res = ProjectTask.Save.save(params, %{id: user.id})
assert res == {:error, :not_found}
end
end