diff --git a/src/DataTables.jl b/src/DataTables.jl
index 7f013d4..334c0c0 100644
--- a/src/DataTables.jl
+++ b/src/DataTables.jl
@@ -72,7 +72,6 @@ export @~,
        tail,
 
        # Remove after deprecation period
-       read_rda,
        pool,
        pool!
 
diff --git a/src/abstractdatatable/abstractdatatable.jl b/src/abstractdatatable/abstractdatatable.jl
index a885136..8ccf630 100644
--- a/src/abstractdatatable/abstractdatatable.jl
+++ b/src/abstractdatatable/abstractdatatable.jl
@@ -659,17 +659,6 @@ unique!(dt)  # modifies dt
 """
 (unique, unique!)
 
-function nonuniquekey(dt::AbstractDataTable)
-    # Here's another (probably a lot faster) way to do `nonunique`
-    # by grouping on all columns. It will fail if columns cannot be
-    # made into CategoricalVector's.
-    gd = groupby(dt, _names(dt))
-    idx = [1:length(gd.idx)][gd.idx][gd.starts]
-    res = fill(true, nrow(dt))
-    res[idx] = false
-    res
-end
-
 # Count the number of missing values in every column of an AbstractDataTable.
 function colmissing(dt::AbstractDataTable) # -> Vector{Int}
     nrows, ncols = size(dt)
@@ -701,7 +690,7 @@ without(dt::AbstractDataTable, c::Any) = without(dt, index(dt)[c])
 
 # catch-all to cover cases where indexing returns a DataTable and copy doesn't
 Base.hcat(dt::AbstractDataTable, x) = hcat!(dt[:, :], x)
-Base.hcat(dt1::AbstractDataTable, dt2::AbstractDataTable) = hcat!(dt[:, :], dt2)
+Base.hcat(dt1::AbstractDataTable, dt2::AbstractDataTable) = hcat!(dt1[:, :], dt2)
 
 Base.hcat(dt::AbstractDataTable, x, y...) = hcat!(hcat(dt, x), y...)
 Base.hcat(dt1::AbstractDataTable, dt2::AbstractDataTable, dtn::AbstractDataTable...) = hcat!(hcat(dt1, dt2), dtn...)
diff --git a/test/cat.jl b/test/cat.jl
index ab4e2ab..52e72ec 100644
--- a/test/cat.jl
+++ b/test/cat.jl
@@ -28,6 +28,23 @@ module TestCat
 
     @test isequal(dt2, DataTables.hcat!(dt2))
 
+    @testset "hcat ::AbstractDataTable" begin
+        dt = DataTable(A = repeat('A':'C', inner=4), B = 1:12)
+        gd = groupby(dt, :A)
+        answer = DataTable(A = fill('A', 4), B = 1:4, A_1 = 'B', B_1 = 5:8, A_2 = 'C', B_2 = 9:12)
+        @test hcat(gd...) == answer
+        answer = answer[1:4]
+        @test hcat(gd[1], gd[2]) == answer
+    end
+
+    @testset "hcat ::Vectors" begin
+        dt = DataTable()
+        DataTables.hcat!(dt, NullableCategoricalVector(1:10))
+        @test isequal(dt[1], NullableCategoricalVector(1:10))
+        DataTables.hcat!(dt, NullableArray(1:10))
+        @test isequal(dt[2], NullableArray(1:10))
+    end
+
     #
     # vcat
     #
diff --git a/test/datatable.jl b/test/datatable.jl
index 6aca8d1..a3eafa1 100644
--- a/test/datatable.jl
+++ b/test/datatable.jl
@@ -379,4 +379,50 @@ module TestDataTable
         b = unstack(dt, :variable, :value)
         @test a == b == DataTable(id = Nullable[1, 2], a = [3, Nullable()], b = [Nullable(), 4])
     end
+
+    @testset "rename" begin
+        dt = DataTable(A = 1:3, B = 'A':'C')
+        @test names(rename(dt, :A, :A_1)) == [:A_1, :B]
+        @test names(dt) == [:A, :B]
+        @test names(rename!(dt, :A, :A_1)) == [:A_1, :B]
+        @test names(dt) == [:A_1, :B]
+    end
+
+    @testset "size" begin
+        dt = DataTable(A = 1:3, B = 'A':'C')
+        @test_throws ArgumentError size(dt, 3)
+        @test length(dt) == 2
+        @test ndims(dt) == 2
+    end
+
+    @testset "description" begin
+        dt = DataTable(A = 1:10)
+        @test head(dt) == DataTable(A = 1:6)
+        @test head(dt, 1) == DataTable(A = 1)
+        @test tail(dt) == DataTable(A = 5:10)
+        @test tail(dt, 1) == DataTable(A = 10)
+    end
+
+    @testset "misc" begin
+        dt = DataTable(Any[collect('A':'C')])
+        @test sprint(dump, dt) == """
+                                  DataTables.DataTable  3 observations of 1 variables
+                                    x1: Array{Char}((3,))
+                                      1: Char A
+                                      2: Char B
+                                      3: Char C
+                                  """
+        dt = DataTable(A = 1:12, B = repeat('A':'C', inner=4))
+        @test DataTables.without(dt, 1) == DataTable(B = repeat('A':'C', inner=4))
+    end
+
+    @testset "column conversions" begin
+        dt = DataTable(Any[collect(1:10), collect(1:10)])
+        @test !isa(dt[1], NullableArray)
+        nullable!(dt, 1)
+        @test isa(dt[1], NullableArray)
+        @test !isa(dt[2], NullableArray)
+        nullable!(dt, [1,2])
+        @test isa(dt[1], NullableArray) && isa(dt[2], NullableArray)
+    end
 end
diff --git a/test/duplicates.jl b/test/duplicates.jl
index 287184f..89b7a04 100644
--- a/test/duplicates.jl
+++ b/test/duplicates.jl
@@ -20,4 +20,9 @@ module TestDuplicates
     @test isequal(updt, unique(pdt))
     unique!(pdt)
     @test isequal(pdt, updt)
+
+    @testset "missing" begin
+        dt = DataTable(A = 1:12, B = repeat('A':'C', inner=4))
+        @test DataTables.colmissing(dt) == [0, 0]
+    end
 end