[R] Fix softprob reshape. (#7126)

R-package/tests/testthat/test_basic.R

@@ -150,6 +150,21 @@ test_that("train and predict softprob", {
 
   mpred1 <- predict(bst, as.matrix(iris[, -5]), reshape = TRUE, iterationrange = c(1, 2))
   expect_equal(mpred, mpred1)
+
+  d <- cbind(
+    x1 = rnorm(100),
+    x2 = rnorm(100),
+    x3 = rnorm(100)
+  )
+  y <- sample.int(10, 100, replace = TRUE) - 1
+  dtrain <- xgb.DMatrix(data = d, info = list(label = y))
+  booster <- xgb.train(
+    params = list(tree_method = "hist"), data = dtrain, nrounds = 4, num_class = 10,
+    objective = "multi:softprob"
+  )
+  predt <- predict(booster, as.matrix(d), reshape = TRUE, strict_shape = FALSE)
+  expect_equal(ncol(predt), 10)
+  expect_equal(rowSums(predt), rep(1, 100), tolerance = 1e-7)
 })
 
 test_that("train and predict softmax", {