Branch :
Map.merge(%{}, %{})
Map.merge(%{a: 1}, %{})
Map.merge(%{}, %{a: 1})
Map.merge(%{a: 1, c: 3}, %{b: 2, d: 4})
Map.merge(%{a: 1, b: 2, c: 3}, %{b: 20, c: 30, d: 40})
Map.merge(%{3 => "left three", 1 => "left one"},
%{2 => "right two", 3 => "right three"})
left = %{a: 1, shared: "left"}
right = %{b: 2, shared: "right"}
merged = Map.merge(left, right)
left
right
merged
Map.count(merged)