Add test for inserting text before selection

test/transforms/fixtures/by-key/insert-text-by-key/before-selection/index.js

@@ -0,0 +1,31 @@
+
+import assert from 'assert'
+
+export default function (state) {
+  const { document, selection } = state
+  const texts = document.getTexts()
+  const firstText = texts.first()
+
+  const nextSelection = selection.merge({
+      anchorKey: firstText.key,
+      focusKey: firstText.key,
+      anchorOffset: 2,
+      focusOffset: 2
+  })
+
+  const next = state
+    .transform()
+    .moveTo(nextSelection)
+    .insertTextByKey(firstText.key, 0, 'XX')
+    .apply()
+
+  assert.deepEqual(
+    next.selection.toJS(),
+    nextSelection.merge({
+      anchorOffset: 4,
+      focusOffset: 4
+    }).toJS()
+  )
+
+  return next
+}

test/transforms/fixtures/by-key/insert-text-by-key/before-selection/input.yaml

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+
+nodes:
+  - kind: block
+    type: paragraph
+    nodes:
+      - kind: text
+        text: hello

test/transforms/fixtures/by-key/insert-text-by-key/before-selection/output.yaml

@@ -0,0 +1,7 @@
+
+nodes:
+  - kind: block
+    type: paragraph
+    nodes:
+      - kind: text
+        text: XXhello