refactor tests and add comments

gtsam/nonlinear/tests/testExpression.cpp

@@ -58,22 +58,23 @@ TEST(Expression, Constant) {
 /* ************************************************************************* */
 // Leaf
 TEST(Expression, Leaf) {
-  Rot3_ R(100);
+  const Key key = 100;
+  Rot3_ R(key);
   Values values;
-  values.insert(100, someR);
+  values.insert(key, someR);
 
   Rot3 actual2 = R.value(values);
   EXPECT(assert_equal(someR, actual2));
 }
 
 /* ************************************************************************* */
-// Many Leaves
+// Test the function `createUnknowns` to create many leaves at once.
 TEST(Expression, Leaves) {
   Values values;
-  Point3 somePoint(1, 2, 3);
+  const Point3 somePoint(1, 2, 3);
   values.insert(Symbol('p', 10), somePoint);
-  std::vector<Point3_> points = createUnknowns<Point3>(10, 'p', 1);
-  EXPECT(assert_equal(somePoint, points.back().value(values)));
+  std::vector<Point3_> pointExpressions = createUnknowns<Point3>(10, 'p', 1);
+  EXPECT(assert_equal(somePoint, pointExpressions.back().value(values)));
 }
 
 /* ************************************************************************* */
@@ -88,29 +89,34 @@ double f2(const Point3& p, OptionalJacobian<1, 3> H) {
 Vector f3(const Point3& p, OptionalJacobian<Eigen::Dynamic, 3> H) {
   return p;
 }
-Point3_ p(1);
+Point3_ pointExpression(1);
 set<Key> expected = list_of(1);
 }  // namespace unary
 
+// Create a unary expression that takes another expression as a single argument.
 TEST(Expression, Unary1) {
   using namespace unary;
-  Expression<Point2> e(f1, p);
-  EXPECT(expected == e.keys());
+  Expression<Point2> unaryExpression(f1, pointExpression);
+  EXPECT(expected == unaryExpression.keys());
 }
+
+// Check that also works with a scalar return value.
 TEST(Expression, Unary2) {
   using namespace unary;
-  Double_ e(f2, p);
-  EXPECT(expected == e.keys());
+  Double_ unaryExpression(f2, pointExpression);
+  EXPECT(expected == unaryExpression.keys());
 }
 
-/* ************************************************************************* */
 // Unary(Leaf), dynamic
 TEST(Expression, Unary3) {
   using namespace unary;
-  //  Expression<Vector> e(f3, p);
+  // TODO(yetongumich): dynamic output arguments do not work yet!
+  // Expression<Vector> unaryExpression(f3, pointExpression);
+  // EXPECT(expected == unaryExpression.keys());
 }
 
 /* ************************************************************************* */
+// Simple test class that implements the `VectorSpace` protocol.
 class Class : public Point3 {
  public:
   enum {dimension = 3};
@@ -133,26 +139,31 @@ template<> struct traits<Class> : public internal::VectorSpace<Class> {};
 // Nullary Method
 TEST(Expression, NullaryMethod) {
   // Create expression
-  Expression<Class> p(67);
-  Expression<double> norm_(p, &Class::norm);
+  const Key key(67);
+  Expression<Class> classExpression(key);
+
+  // Make expression from a class method, note how it differs from the function
+  // expressions by leading with the class expression in the constructor.
+  Expression<double> norm_(classExpression, &Class::norm);
 
   // Create Values
   Values values;
-  values.insert(67, Class(3, 4, 5));
+  values.insert(key, Class(3, 4, 5));
 
   // Check dims as map
   std::map<Key, int> map;
-  norm_.dims(map);
+  norm_.dims(map); // TODO(yetongumich): Change to google style pointer convention.
   LONGS_EQUAL(1, map.size());
 
   // Get value and Jacobians
   std::vector<Matrix> H(1);
   double actual = norm_.value(values, H);
 
   // Check all
-  EXPECT(actual == sqrt(50));
+  const double norm = sqrt(3*3 + 4*4 + 5*5);
+  EXPECT(actual == norm);
   Matrix expected(1, 3);
-  expected << 3.0 / sqrt(50.0), 4.0 / sqrt(50.0), 5.0 / sqrt(50.0);
+  expected << 3.0 / norm, 4.0 / norm, 5.0 / norm;
   EXPECT(assert_equal(expected, H[0]));
 }
 
@@ -170,29 +181,29 @@ Point3_ p_cam(x, &Pose3::transformTo, p);
 }
 
 /* ************************************************************************* */
-// Check that creating an expression to double compiles
+// Check that creating an expression to double compiles.
 TEST(Expression, BinaryToDouble) {
   using namespace binary;
   Double_ p_cam(doubleF, x, p);
 }
 
 /* ************************************************************************* */
-// keys
+// Check keys of an expression created from class method.
 TEST(Expression, BinaryKeys) {
   set<Key> expected = list_of(1)(2);
   EXPECT(expected == binary::p_cam.keys());
 }
 
 /* ************************************************************************* */
-// dimensions
+// Check dimensions by calling `dims` method.
 TEST(Expression, BinaryDimensions) {
   map<Key, int> actual, expected = map_list_of<Key, int>(1, 6)(2, 3);
   binary::p_cam.dims(actual);
   EXPECT(actual == expected);
 }
 
 /* ************************************************************************* */
-// dimensions
+// Check dimensions by calling `traceSize` method.
 TEST(Expression, BinaryTraceSize) {
   typedef internal::BinaryExpression<Point3, Pose3, Point3> Binary;
   size_t expectedTraceSize = sizeof(Binary::Record);
@@ -247,6 +258,7 @@ TEST(Expression, TreeTraceSize) {
 }
 
 /* ************************************************************************* */
+// Test compose operation with * operator.
 TEST(Expression, compose1) {
   // Create expression
   Rot3_ R1(1), R2(2);
@@ -258,7 +270,7 @@ TEST(Expression, compose1) {
 }
 
 /* ************************************************************************* */
-// Test compose with arguments referring to the same rotation
+// Test compose with arguments referring to the same rotation.
 TEST(Expression, compose2) {
   // Create expression
   Rot3_ R1(1), R2(1);
@@ -270,7 +282,7 @@ TEST(Expression, compose2) {
 }
 
 /* ************************************************************************* */
-// Test compose with one arguments referring to constant rotation
+// Test compose with one arguments referring to constant rotation.
 TEST(Expression, compose3) {
   // Create expression
   Rot3_ R1(Rot3::identity()), R2(3);
@@ -282,7 +294,7 @@ TEST(Expression, compose3) {
 }
 
 /* ************************************************************************* */
-// Test with ternary function
+// Test with ternary function.
 Rot3 composeThree(const Rot3& R1, const Rot3& R2, const Rot3& R3, OptionalJacobian<3, 3> H1,
                   OptionalJacobian<3, 3> H2, OptionalJacobian<3, 3> H3) {
   // return dummy derivatives (not correct, but that's ok for testing here)
@@ -306,6 +318,7 @@ TEST(Expression, ternary) {
 }
 
 /* ************************************************************************* */
+// Test scalar multiplication with * operator.
 TEST(Expression, ScalarMultiply) {
   const Key key(67);
   const Point3_ expr = 23 * Point3_(key);
@@ -336,6 +349,7 @@ TEST(Expression, ScalarMultiply) {
 }
 
 /* ************************************************************************* */
+// Test sum with + operator.
 TEST(Expression, BinarySum) {
   const Key key(67);
   const Point3_ sum_ = Point3_(key) + Point3_(Point3(1, 1, 1));
@@ -366,6 +380,7 @@ TEST(Expression, BinarySum) {
 }
 
 /* ************************************************************************* */
+// Test sum of 3 variables with + operator.
 TEST(Expression, TripleSum) {
   const Key key(67);
   const Point3_ p1_(Point3(1, 1, 1)), p2_(key);
@@ -387,6 +402,7 @@ TEST(Expression, TripleSum) {
 }
 
 /* ************************************************************************* */
+// Test sum with += operator.
 TEST(Expression, PlusEqual) {
   const Key key(67);
   const Point3_ p1_(Point3(1, 1, 1)), p2_(key);
@@ -454,18 +470,19 @@ TEST(Expression, UnaryOfSum) {
 /* ************************************************************************* */
 TEST(Expression, WeightedSum) {
   const Key key1(42), key2(67);
+  const Point3 point1(1, 0, 0), point2(0, 1, 0);
   const Point3_ weighted_sum_ = 17 * Point3_(key1) + 23 * Point3_(key2);
 
   map<Key, int> actual_dims, expected_dims = map_list_of<Key, int>(key1, 3)(key2, 3);
   weighted_sum_.dims(actual_dims);
   EXPECT(actual_dims == expected_dims);
 
   Values values;
-  values.insert<Point3>(key1, Point3(1, 0, 0));
-  values.insert<Point3>(key2, Point3(0, 1, 0));
+  values.insert<Point3>(key1, point1);
+  values.insert<Point3>(key2, point2);
 
   // Check value
-  const Point3 expected = 17 * Point3(1, 0, 0) + 23 * Point3(0, 1, 0);
+  const Point3 expected = 17 * point1 + 23 * point2;
   EXPECT(assert_equal(expected, weighted_sum_.value(values)));
 
   // Check value + Jacobians