refactor: Move scroller into own testable module

lua/tests/automated/scroller_spec.lua

@@ -0,0 +1,56 @@
+local p_scroller = require('telescope.pickers.scroller')
+
+local eq = assert.are.same
+
+describe('scroller', function()
+  local max_results = 10
+
+  describe('cycle', function()
+    local cycle_scroller = p_scroller.create('cycle')
+
+    it('should return values within the max results', function()
+      eq(5, cycle_scroller(max_results, max_results, 5))
+    end)
+
+    it('should return 0 at 0', function()
+      eq(0, cycle_scroller(max_results, max_results, 0))
+    end)
+
+    it('should cycle you to the top when you go below 0', function()
+      eq(max_results - 1, cycle_scroller(max_results, max_results, -1))
+    end)
+
+    it('should cycle you to 0 when you go past the results', function()
+      eq(0, cycle_scroller(max_results, max_results, max_results + 1))
+    end)
+
+    it('should cycle when current results is less than max_results', function()
+      eq(0, cycle_scroller(max_results, 5, 7))
+    end)
+  end)
+
+  describe('other', function()
+    local limit_scroller = p_scroller.create('limit')
+
+    it('should return values within the max results', function()
+      eq(5, limit_scroller(max_results, max_results, 5))
+    end)
+
+    it('should return 0 at 0', function()
+      eq(0, limit_scroller(max_results, max_results, 0))
+    end)
+
+    it('should not cycle', function()
+      eq(0, limit_scroller(max_results, max_results, -1))
+    end)
+
+    it('should cycle you to 0 when you go past the results', function()
+      eq(max_results - 1, limit_scroller(max_results, max_results, max_results + 1))
+    end)
+
+    it('should stay at current results when current results is less than max_results', function()
+      local current = 5
+      eq(current - 1, limit_scroller(max_results, current, 7))
+    end)
+  end)
+end)