Add automated tests for some mods (#605)

Depends on mineunit from https://github.com/S-S-X/mineunit

mesecons, mesecons_mvps, mesecons_fpga, and mesecons_luacontroller are now tested.

mesecons_luacontroller/spec/lightweight_interrupt_spec.lua

@@ -0,0 +1,38 @@
+require("mineunit")
+
+-- This test is done in a separate file since it requires different configuration at startup.
+mineunit("core")
+minetest.settings:set("mesecon.luacontroller_lightweight_interrupts", "true")
+
+fixture("mesecons_luacontroller")
+
+describe("LuaController lightweight interrupt", function()
+	local pos = {x = 0, y = 0, z = 0}
+
+	before_each(function()
+		mesecon._test_place(pos, "mesecons_luacontroller:luacontroller0000")
+		mineunit:execute_globalstep() -- Execute receptor_on action
+	end)
+
+	after_each(function()
+		mesecon._test_reset()
+		world.clear()
+	end)
+
+	it("works", function()
+		mesecon._test_program_luac(pos, [[
+			if event.type == "program" then
+				interrupt(5)
+				interrupt(10)
+			elseif event.type == "interrupt" then
+				port.a = not pin.a
+			end
+		]])
+		mineunit:execute_globalstep(0.1)
+		mineunit:execute_globalstep(9)
+		assert.equal("mesecons_luacontroller:luacontroller0000", world.get_node(pos).name)
+		mineunit:execute_globalstep(1)
+		mineunit:execute_globalstep(0.1)
+		assert.equal("mesecons_luacontroller:luacontroller0001", world.get_node(pos).name)
+	end)
+end)