test: Check the context line seen through n steps after calling setCo…

…ntextLineNumber.

test/fixtures/debugger/twenty-lines.js

@@ -0,0 +1,20 @@
+let x = 0;
+x = 1;
+x = 2;
+x = 3;
+x = 4;
+x = 5;
+x = 6;
+x = 7;
+x = 8;
+x = 9;
+x = 10;
+x = 11;
+x = 12;
+x = 13;
+x = 14;
+x = 15;
+x = 16;
+x = 17;
+x = 18;
+module.exports = x;

test/sequential/test-debugger-set-context-line-number.mjs

@@ -0,0 +1,41 @@
+import { skipIfInspectorDisabled } from '../common/index.mjs';
+skipIfInspectorDisabled();
+
+import { path } from '../common/fixtures.mjs';
+import startCLI from '../common/debugger.js';
+
+import assert from 'assert';
+
+const script = path('debugger', 'twenty-lines.js');
+const cli = startCLI([script]);
+
+function onFatal(error) {
+  cli.quit();
+  throw error;
+}
+
+// Stepping through breakpoints.
+try {
+  await cli.waitForInitialBreak();
+  await cli.waitForPrompt();
+
+  // Make sure the initial value is 2.
+  await cli.stepCommand('n');
+  assert.ok(cli.output.includes("4 x = 3;"));
+
+  await cli.command('setContextLineNumber(5)');
+  await cli.stepCommand('n');
+  assert.ok(cli.output.includes("8 x = 7;"));
+
+  await cli.command('setContextLineNumber(3)');
+  await cli.stepCommand('n');
+  assert.ok(cli.output.includes("7 x = 6;"));
+
+  await cli.command('list(3)');
+  await cli.stepCommand('n');
+  assert.ok(cli.output.includes("7 x = 6;"));
+
+  await cli.quit();
+} catch (error) {
+  onFatal(error);
+}