Expand test framework and test cases (#685)

* Fix comment

* Ekf wrapper for testing

Add utility function for accessing information in the ekf object

* Add step function for Gps sensor

* Add RangeFinder and Flow to simulated sensors

* Add first fusion logic tests

* Add units to function name

* Use EXPECT_TRUE

* Adding missing qualifiers

* Improve EXPECT_ calls

* Improve naming

test/sensor_simulator/flow.cpp

@@ -0,0 +1,38 @@
+#include "flow.h"
+
+namespace sensor_simulator
+{
+namespace sensor
+{
+
+Flow::Flow(std::shared_ptr<Ekf> ekf):Sensor(ekf)
+{
+}
+
+Flow::~Flow()
+{
+}
+
+void Flow::send(uint32_t time)
+{
+	_ekf->setOpticalFlowData(time, &_flow_data);
+}
+
+void Flow::setData(const flow_message& flow)
+{
+	_flow_data = flow;
+
+}
+
+flow_message Flow::dataAtRest()
+{
+	flow_message _flow_at_rest;
+	_flow_at_rest.dt = 20000;
+	_flow_at_rest.flowdata = Vector2f{0.0f, 0.0f};
+	_flow_at_rest.gyrodata = Vector3f{0.0f, 0.0f, 0.0f};
+	_flow_at_rest.quality = 255;
+	return _flow_at_rest;
+}
+
+} // namespace sensor
+} // namespace sensor_simulator