Add tests for ScrollLineUpAction

src/com/maddyhome/idea/vim/helper/EditorHelper.java

@@ -679,7 +679,7 @@ public class EditorHelper {
     int y = editor.visualLineToY(visualLine);
     int height = inlayHeight + editor.getLineHeight() + exPanelHeight;
     Rectangle visibleArea = getVisibleArea(editor);
-    return scrollVertically(editor, y - visibleArea.height + height);
+    return scrollVertically(editor, max(0, y - visibleArea.height + height));
   }
 
   /**

test/org/jetbrains/plugins/ideavim/action/scroll/ScrollLineUpActionTest.kt

@@ -0,0 +1,99 @@
+/*
+ * IdeaVim - Vim emulator for IDEs based on the IntelliJ platform
+ * Copyright (C) 2003-2020 The IdeaVim authors
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.jetbrains.plugins.ideavim.action.scroll
+
+import com.maddyhome.idea.vim.helper.StringHelper.parseKeys
+import com.maddyhome.idea.vim.option.OptionsManager
+import org.jetbrains.plugins.ideavim.VimTestCase
+
+// |<C-Y>|
+class ScrollLineUpActionTest : VimTestCase() {
+  fun `test scroll single line up`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 29)
+    typeText(parseKeys("<C-Y>"))
+    assertPosition(29, 0)
+    assertVisibleArea(28, 62)
+  }
+
+  fun `test scroll line up will keep cursor on screen`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 63)
+    typeText(parseKeys("<C-Y>"))
+    assertPosition(62, 0)
+    assertVisibleArea(28, 62)
+  }
+
+  fun `test scroll count lines up`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 29)
+    typeText(parseKeys("10<C-Y>"))
+    assertPosition(29, 0)
+    assertVisibleArea(19, 53)
+  }
+
+  fun `test scroll count lines up will keep cursor on screen`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 63)
+    typeText(parseKeys("10<C-Y>"))
+    assertPosition(53, 0)
+    assertVisibleArea(19, 53)
+  }
+
+  fun `test too many lines up stops at zero`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 29)
+    typeText(parseKeys("100<C-Y>"))
+    assertPosition(29, 0)
+    assertVisibleArea(0, 34)
+  }
+
+  fun `test too many lines up stops at zero and keeps cursor on screen`() {
+    configureByPages(5)
+    setPositionAndScroll(59, 59)
+    typeText(parseKeys("100<C-Y>"))
+    assertPosition(34, 0)
+    assertVisibleArea(0, 34)
+  }
+
+  fun `test scroll up uses scrolloff and moves cursor`() {
+    OptionsManager.scrolloff.set(10)
+    configureByPages(5)
+    setPositionAndScroll(20, 44)
+    typeText(parseKeys("<C-Y>"))
+    assertPosition(43, 0)
+    assertVisibleArea(19, 53)
+  }
+
+  fun `test scroll up is not affected by scrolljump`() {
+    OptionsManager.scrolljump.set(10)
+    configureByPages(5)
+    setPositionAndScroll(29, 63)
+    typeText(parseKeys("<C-Y>"))
+    assertPosition(62, 0)
+    assertVisibleArea(28, 62)
+  }
+
+  fun `test scroll line up in visual mode`() {
+    configureByPages(5)
+    setPositionAndScroll(29, 29)
+    typeText(parseKeys("Vjjjj", "<C-Y>"))
+    assertVisibleArea(28, 62)
+  }
+}