add tests

Author: Mukulyadav2004

R/fwrite.R

@@ -41,7 +41,7 @@ fwrite = function(x, file="", append=FALSE, quote="auto",
     }
   }
   # Handle select argument using .shallow()
-  if (!null(select)) {
+  if (!is.null(select)) {
     cols = colnamesInt(x, select)
     if (is.data.table(x)) {
       x = .shallow(x, cols)

inst/tests/tests.Rraw

@@ -21608,4 +21608,13 @@ DT = data.table(a=1:2, b=3:4)
 f = tempfile()
 fwrite(DT, f, select = "a") 
 test(2338.1, names(fread(f)), "a")
+df = as.data.frame(DT)
+fwrite(df, f, select = "a")
+test(2338.2, names(fread(f)), "a")
+l = as.list(DT)
+fwrite(l, f, select = "a")
+test(2338.3, names(fread(f)), "a")
+m = as.matrix(DT)
+fwrite(m, f, select = "a")
+test(2338.4, names(fread(f)), "a")
 unlink(f)