WIP line tests

geometry_test.go

@@ -954,8 +954,10 @@ func TestLine_Formula(t *testing.T) {
 				t.Errorf("Line.Formula() gotM = %v, want %v", gotM, tt.wantM)
 			}
 			if gotB != tt.wantB {
+				if math.IsNaN(tt.wantB) && !math.IsNaN(gotB) {
 					t.Errorf("Line.Formula() gotB = %v, want %v", gotB, tt.wantB)
 				}
+			}
 		})
 	}
 }