Add initial support for signal generators

test/test_signal_generator.py

+from b_asic.signal_generator import Constant, Impulse, Step
+
+
+def test_impulse():
+    g = Impulse()
+    assert g(0) == 1
+    assert g(1) == 0
+    assert g(2) == 0
+
+    g = Impulse(1)
+    assert g(0) == 0
+    assert g(1) == 1
+    assert g(2) == 0
+
+
+def test_step():
+    g = Step()
+    assert g(0) == 1
+    assert g(1) == 1
+    assert g(2) == 1
+
+    g = Step(1)
+    assert g(0) == 0
+    assert g(1) == 1
+    assert g(2) == 1
+
+
+def test_constant():
+    g = Constant()
+    assert g(0) == 1
+    assert g(1) == 1
+    assert g(2) == 1
+
+    g = Constant(0.5)
+    assert g(0) == 0.5
+    assert g(1) == 0.5
+    assert g(2) == 0.5
+
+
+def test_addition():
+    g = Impulse() + Impulse(2)
+    assert g(0) == 1
+    assert g(1) == 0
+    assert g(2) == 1
+    assert g(3) == 0
+
+    g = 1 + Impulse(2)
+    assert g(0) == 1
+    assert g(1) == 1
+    assert g(2) == 2
+    assert g(3) == 1
+
+    g = Impulse(1) + 1
+    assert g(0) == 1
+    assert g(1) == 2
+    assert g(2) == 1
+    assert g(3) == 1
+
+
+def test_subtraction():
+    g = Impulse() - Impulse(2)
+    assert g(0) == 1
+    assert g(1) == 0
+    assert g(2) == -1
+    assert g(3) == 0
+
+    g = 1 - Impulse(2)
+    assert g(0) == 1
+    assert g(1) == 1
+    assert g(2) == 0
+    assert g(3) == 1
+
+    g = Impulse(2) - 1
+    assert g(0) == -1
+    assert g(1) == -1
+    assert g(2) == 0
+    assert g(3) == -1
+
+
+def test_multiplication():
+    g = Impulse() * 0.5
+    assert g(0) == 0.5
+    assert g(1) == 0
+    assert g(2) == 0