Add fourslash tests

src/services/refactors/moveToNewFile.ts

@@ -510,7 +510,12 @@ namespace ts.refactor {
             }
 
             const jsxNamespace = checker.getJsxNamespace(containsJsx);
+
+            // Strictly speaking, this could resolve to a symbol other than the JSX namespace.
+            // This will produce erroneous output (probably, an incorrectly copied import) but
+            // is expected to be very rare and easily reversible.
             const jsxNamespaceSymbol = checker.resolveName(jsxNamespace, containsJsx, SymbolFlags.Namespace, /*excludeGlobals*/ true);
+
             return !!jsxNamespaceSymbol && some(jsxNamespaceSymbol.declarations, isInImport)
                 ? jsxNamespaceSymbol
                 : undefined;

tests/cases/fourslash/moveToNewFile_moveJsxImport1.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// @jsx: preserve
+// @noLib: true
+// @libFiles: react.d.ts,lib.d.ts
+
+// @Filename: file.tsx
+//// import React = require('react');
+//// [|<div/>;|]
+//// 1;
+
+verify.moveToNewFile({
+    newFileContents: {
+        "/tests/cases/fourslash/file.tsx":
+`1;`,
+        "/tests/cases/fourslash/newFile.tsx":
+`import React = require('react');
+<div />;
+`,
+    }
+});

tests/cases/fourslash/moveToNewFile_moveJsxImport2.ts

@@ -0,0 +1,22 @@
+/// <reference path='fourslash.ts' />
+
+// @jsx: preserve
+// @noLib: true
+// @libFiles: react.d.ts,lib.d.ts
+
+// @Filename: file.tsx
+//// import React = require('react');
+//// [|<div/>;|]
+//// <div/>;
+
+verify.moveToNewFile({
+    newFileContents: {
+        "/tests/cases/fourslash/file.tsx":
+`import React = require('react');
+<div/>;`,
+        "/tests/cases/fourslash/newFile.tsx":
+`import React = require('react');
+<div />;
+`,
+    }
+});

tests/cases/fourslash/moveToNewFile_moveJsxImport3.ts

@@ -0,0 +1,21 @@
+/// <reference path='fourslash.ts' />
+
+// @jsx: preserve
+// @noLib: true
+// @libFiles: react.d.ts,lib.d.ts
+
+// @Filename: file.tsx
+//// import React = require('react');
+//// [|1;|]
+//// <div/>;
+
+verify.moveToNewFile({
+    newFileContents: {
+        "/tests/cases/fourslash/file.tsx":
+`import React = require('react');
+<div/>;`,
+        "/tests/cases/fourslash/newFile.tsx":
+`1;
+`,
+    }
+});