Add testCacheMatrix.R in a location that doesn't give the assignment …

…code away.

resources/testMakeCacheMatrix.R

@@ -0,0 +1,56 @@
+#
+# rprog-testCacheMatrix.R
+#
+# test script for makeCacheMatrix.R
+# 
+
+# approach 1: create a matrix object, then use it as input to cacheSolve()
+
+a <- makeCacheMatrix(matrix(c(-1, -2, 1, 1), 2,2))
+cacheSolve(a)
+
+# call cacheSolve(a) a second time to trigger the "getting cached inverse" message
+cacheSolve(a)
+
+# multiply the matrix by inverse, resulting in identity matrix
+a$get() %*% a$getsolve()
+
+# reset a with another matrix to clear out cached value
+a$set(matrix(c(2,3,2,2),2,2))
+
+# confirm that a has new data and that cache is NULL
+a$get()
+a$getsolve()
+
+# rerun cache solve, note that "getting cached inverse" does not print,
+# and that we get a different result
+cacheSolve(a)
+
+# approach 2: use makeCacheMatrix() as the input argument to cacheSolve()
+#             note that the argument to cacheSolve() is a different object
+#             than the argument to the first call of cacheSolve()
+cacheSolve(makeCacheMatrix(matrix(c(-1, -2, 1, 1), 2,2)))
+
+# try a non-invertible matrix
+b <- makeCacheMatrix(matrix(c(0,0,0,0),2,2))
+cacheSolve(b)
+
+# illustrate getting the memory locations
+a <- makeCacheMatrix(matrix(c(-1, -2, 1, 1), 2,2))
+tracemem(a)
+tracemem(matrix(c(-1, -2, 1, 1), 2,2))
+
+# approach 2: use makeCacheMatrix() as the input argument to cacheSolve()
+#             note that the argument to cacheSolve() is a different object
+#             than the argument to the first call of cacheSolve()
+cacheSolve(makeCacheMatrix(matrix(c(-1, -2, 1, 1), 2,2)))
+
+# illustrate getting the memory locations
+a <- makeCacheMatrix(matrix(c(-1, -2, 1, 1), 2,2))
+tracemem(a)
+tracemem(matrix(c(-1, -2, 1, 1), 2,2))
+
+# test non-matrix input: should return "not a matrix" error
+
+a$set(1:5)
+cacheSolve(a)