tests/testthat/test-cov-robust.R

In nlmixr2est: Nonlinear Mixed Effects Models in Population PK/PD, Estimation Routines

nmTest({
  test_that(".nlmixr2RobustCov handles full-rank matrices like the plain QR solve", {
    .testSeed(42)
    X <- matrix(rnorm(40), ncol = 4)
    expected <- solve(crossprod(X))
    got <- nlmixr2est:::.nlmixr2RobustCov(X)
    expect_equal(unname(got), unname(expected), tolerance = 1e-6)
  })

  test_that(".nlmixr2RobustCov degrades only the ill-identified parameter(s)", {
    .testSeed(42)
    X <- matrix(rnorm(40), ncol = 4)
    # Zero out one column -- unidentifiable, should not blow up the others
    X[, 3] <- 0
    got <- nlmixr2est:::.nlmixr2RobustCov(X)
    expect_equal(dim(got), c(4L, 4L))
    expect_true(all(is.na(got[3, ])))
    expect_true(all(is.na(got[, 3])))
    # The well-identified 3x3 submatrix should match a direct solve
    keep <- c(1, 2, 4)
    expected <- solve(crossprod(X[, keep, drop = FALSE]))
    expect_equal(unname(got[keep, keep]), unname(expected), tolerance = 1e-6)
  })

  test_that(".nlmixr2RobustCov returns all-NA when nothing is identifiable", {
    X <- matrix(0, nrow = 10, ncol = 3)
    got <- nlmixr2est:::.nlmixr2RobustCov(X)
    expect_true(all(is.na(got)))
    expect_equal(dim(got), c(3L, 3L))
  })

  test_that(".nlmixr2CholPartial validates only the finite submatrix", {
    covm <- diag(c(1, 2, 3))
    dimnames(covm) <- list(c("a", "b", "c"), c("a", "b", "c"))
    # Fully finite, positive-definite: behaves like chol()
    expect_false(inherits(nlmixr2est:::.nlmixr2CholPartial(covm), "try-error"))

    covm2 <- covm
    covm2[2, ] <- NA_real_
    covm2[, 2] <- NA_real_
    # NA row/col for one parameter, rest still positive-definite: still valid
    expect_false(inherits(nlmixr2est:::.nlmixr2CholPartial(covm2), "try-error"))

    covm3 <- covm
    covm3[1, 1] <- -1 # not positive-definite even ignoring NA
    expect_true(inherits(nlmixr2est:::.nlmixr2CholPartial(covm3), "try-error"))

    covm4 <- matrix(NA_real_, 2, 2)
    expect_true(inherits(nlmixr2est:::.nlmixr2CholPartial(covm4), "try-error"))
  })
})