Added more tests for Filter and Field classes.

backtester/test/datahandler/test_filter.py

@@ -50,6 +50,7 @@ def test_compose_filters_with_or():
 
 
 def test_compose_many_filters():
+    """Test composition of three filters mixing and + or"""
     symbol_field = Field("underlying", "underlying")
     strike_field = Field("strike", "strike")
     ft1 = symbol_field == "SPX"
@@ -57,3 +58,43 @@ def test_compose_many_filters():
     ft3 = strike_field < 100
     composed = ft1 & (ft2 | ft3)
     assert composed.query == "(underlying == 'SPX') & (((strike >= 200) | (strike < 100)))"
+
+
+def test_add_number_to_field():
+    """Test addition of a number to a field"""
+    strike_field = Field("strike", "strike")
+    field = strike_field + 10
+    assert field.name == "strike + 10"
+    assert field.mapping == "strike + 10"
+
+
+def test_subtract_number_from_field():
+    """Test subtraction of a number from a field"""
+    strike_field = Field("strike", "strike")
+    field = strike_field - 10
+    assert field.name == "strike - 10"
+    assert field.mapping == "strike - 10"
+
+
+def test_multiply_field_by_number():
+    """Test multiplication of a field by a number"""
+    underlying_last = Field("last", "underlying_last")
+    field = underlying_last * 1.5
+    assert field.name == "last * 1.5"
+    assert field.mapping == "underlying_last * 1.5"
+
+
+def test_multiply_on_left():
+    """Test multiplication of a field by a number on the *left*"""
+    underlying_last = Field("last", "underlying_last")
+    field = 1.5 * underlying_last
+    assert field.name == "1.5 * last"
+    assert field.mapping == "1.5 * underlying_last"
+
+
+def test_filter_from_combined_field():
+    """Test filter from a linear combination of fields"""
+    underlying_last = Field("last", "underlying_last")
+    strike_field = Field("strike", "strike")
+    combined_filter = underlying_last == strike_field * 1.2
+    assert combined_filter.query == "underlying_last == strike * 1.2"