diff --git a/rtl/sampler/tests/sampler_main_tb.sv b/rtl/sampler/tests/sampler_main_tb.sv
new file mode 100644
index 0000000..6ee619a
--- /dev/null
+++ b/rtl/sampler/tests/sampler_main_tb.sv
@@ -0,0 +1,132 @@
+`timescale 1ns / 1ps
+
+module sampler_tb;
+
+    parameter DATA_WIDTH   = 12;
+    parameter PROCESS_MODE = 0;
+    parameter CLK_PERIOD   = 15.3846;
+    parameter TEST_NUM     = 1000;
+
+    logic clk;
+    logic rst;
+
+    logic [DATA_WIDTH-1:0] data_in;
+    logic out_of_range;
+
+    logic [DATA_WIDTH-1:0] m_axis_tdata;
+    logic m_axis_tvalid;
+
+    integer errors = 0;
+
+    sampler #(
+        .DATA_WIDTH(DATA_WIDTH),
+        .PROCESS_MODE(PROCESS_MODE)
+    ) dut (
+        .clk_in(clk),
+        .rst(rst),
+        .data_in(data_in),
+        .out_of_range(out_of_range),
+        .m_axis_tdata(m_axis_tdata),
+        .m_axis_tvalid(m_axis_tvalid)
+    );
+
+    initial begin
+        clk = 0;
+        forever #(CLK_PERIOD/2) clk = ~clk;
+    end
+
+    function automatic [DATA_WIDTH-1:0] ref_convert(input [DATA_WIDTH-1:0] din);
+        if (PROCESS_MODE == 0)
+            return din;
+        else if (din == {1'b1, {(DATA_WIDTH-1){1'b0}}})
+            return din;
+        else
+            return din[DATA_WIDTH-1] ?
+                   {1'b1, (~din[DATA_WIDTH-2:0] + 1'b1)} :
+                   din;
+    endfunction
+
+    task send(input [DATA_WIDTH-1:0] word, input bit oor);
+        @(posedge clk);
+        data_in      <= word;
+        out_of_range <= oor;
+    endtask
+
+    logic [DATA_WIDTH-1:0] exp_d0, exp_d1, exp_d2;
+    logic oor_d0, oor_d1, oor_d2;
+
+    initial begin
+        $display("\n=== RANDOM SAMPLER TEST===\n");
+
+        rst = 1;
+        data_in = 0;
+        out_of_range = 0;
+
+        exp_d0 = 0;
+        exp_d1 = 0;
+        exp_d2 = 0;
+
+        oor_d0 = 1;
+        oor_d1 = 1;
+        oor_d2 = 1;
+
+        repeat(5) @(posedge clk);
+        rst = 0;
+        repeat(2) @(posedge clk);
+
+        repeat (TEST_NUM) begin
+            logic [DATA_WIDTH-1:0] rand_data;
+            bit rand_oor;
+
+            rand_data = $urandom_range(0, (1 << DATA_WIDTH) - 1);
+            rand_oor  = ($urandom_range(0, 99) < 20);
+
+            @(negedge clk);
+
+            if (!oor_d2) begin
+                if (m_axis_tvalid !== 1) begin
+                    $display("ERROR: valid=0");
+                    errors++;
+                end
+
+                if (m_axis_tdata !== exp_d2) begin
+                    $display("ERROR: data mismatch");
+                    $display(" expected = %h", exp_d2);
+                    $display(" got      = %h", m_axis_tdata);
+                    errors++;
+                end
+            end
+
+            send(rand_data, rand_oor);
+
+            exp_d2 = exp_d1;
+            exp_d1 = exp_d0;
+            exp_d0 = ref_convert(rand_data);
+
+            oor_d2 = oor_d1;
+            oor_d1 = oor_d0;
+            oor_d0 = rand_oor;
+        end
+
+        @(posedge clk);
+
+
+        if (!oor_d2) begin
+        
+            if (m_axis_tdata !== exp_d2) begin
+                $display("ERROR: final mismatch");
+                $display(" expected = %h", exp_d2);
+                $display(" got      = %h", m_axis_tdata);
+                errors++;
+            end
+        end
+
+        if (errors == 0)
+            $display("\n========== ALL PASSED ==========\n");
+        else
+            $display("\n========== FAILED: %0d errors ==========\n", errors);
+
+        $finish;
+    end
+
+endmodule
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