Add basic SVD equivalence test

Author: alexpghayes

DESCRIPTION

@@ -1,10 +1,10 @@
 Package: sparseLRMatrix
 Title: Represent and Use Sparse + Low Rank Matrices
-Version: 0.0.0.9001
+Version: 0.0.0.9002
 Authors@R: 
     person(given = "Alex",
            family = "Hayes",
-           role = c("aut", "cre"),
+           role = c("aut", "cre", "cph"),
            email = "alexpghayes@gmail.com",
            comment = c(ORCID = "0000-0002-4985-5160"))
 Description: Provides an S4 class for representing and
@@ -24,4 +24,6 @@ RoxygenNote: 7.1.1.9000
 URL: https://rohelab.github.io/sparseLRMatrix, https://github.com/RoheLab/sparseLRMatrix
 BugReports: https://github.com/RoheLab/sparseLRMatrix/issues
 Suggests: 
-    covr
+    covr,
+    testthat (>= 3.0.0)
+Config/testthat/edition: 3

tests/testthat.R

@@ -0,0 +1,4 @@
+library(testthat)
+library(sparseLRMatrix)
+
+test_check("sparseLRMatrix")

tests/testthat/test-svds-matches.R

@@ -0,0 +1,23 @@
+test_that("singular values match", {
+
+  set.seed(528491)
+
+  n <- 50
+  m <- 40
+  k <- 3
+
+  A <- rsparsematrix(n, m, 0.1)
+
+  U <- Matrix(rnorm(n * k), nrow = n, ncol = k)
+  V <- Matrix(rnorm(m * k), nrow = m, ncol = k)
+
+  # construct the matrix, which represents A + U %*% t(V)
+  X <- sparseLRMatrix(sparse = A, U = U, V = V)
+
+  s <- svds(X, 5)  # efficient
+
+  Y <- A + tcrossprod(U, V)
+  s2 <- svds(Y, 5)  # inefficient, but same calculation
+
+  expect_equal(s, s2)
+})