[SPARK-31372][SQL][TEST][FOLLOW-UP] Improve ExpressionsSchemaSuite so that easy to track the diff.

sql/core/src/test/scala/org/apache/spark/sql/ExpressionsSchemaSuite.scala

@@ -136,38 +136,39 @@ class ExpressionsSchemaSuite extends QueryTest with SharedSparkSession {
       }
     }
 
+    val header = Seq(
+      s"<!-- Automatically generated by${getClass.getSimpleName} -->",
+      "## Summary",
+      s"  - Number of queries: ${outputs.size}",
+      s"  - Number of expressions that missing example: ${missingExamples.size}",
+      s"  - Expressions missing examples: ${missingExamples.mkString(",")}",
+      "## Schema of Built-in Functions",
+      "| Class name | Function name or alias | Query example | Output schema |",
+      "| ---------- | ---------------------- | ------------- | ------------- |"
+    )
+
     if (regenerateGoldenFiles) {
-      val missingExampleStr = missingExamples.mkString(",")
-      val goldenOutput = {
-        s"<!-- Automatically generated by${getClass.getSimpleName} -->\n" +
-        "## Summary\n" +
-        s"  - Number of queries: ${outputs.size}\n" +
-        s"  - Number of expressions that missing example: ${missingExamples.size}\n" +
-        s"  - Expressions missing examples: $missingExampleStr\n" +
-        "## Schema of Built-in Functions\n" +
-        "| Class name | Function name or alias | Query example | Output schema |\n" +
-        "| ---------- | ---------------------- | ------------- | ------------- |\n" +
-        outputBuffer.mkString("\n")
-      }
+      val goldenOutput = (header ++ outputBuffer).mkString("\n")
       val parent = resultFile.getParentFile
       if (!parent.exists()) {
         assert(parent.mkdirs(), "Could not create directory: " + parent)
       }
       stringToFile(resultFile, goldenOutput)
     }
 
+    val outputSize = outputs.size
+    val headerSize = header.size
     val expectedOutputs: Seq[QueryOutput] = {
-      val goldenOutput = fileToString(resultFile)
-      val lines = goldenOutput.split("\n")
+      val expectedGoldenOutput = fileToString(resultFile)
+      val lines = expectedGoldenOutput.split("\n")
+      val expectedSize = lines.size
 
-      // The header of golden file has one line, plus four lines of the summary and three
-      // lines of the header of schema table.
-      assert(lines.size == outputs.size + 8,
-        s"Expected ${outputs.size + 8} blocks in result file but got ${lines.size}. " +
-          s"Try regenerate the result files.")
+      assert(expectedSize == outputSize + headerSize,
+        s"Expected $expectedSize blocks in result file but got " +
+          s"${outputSize + headerSize}. Try regenerate the result files.")
 
-      Seq.tabulate(outputs.size) { i =>
-        val segments = lines(i + 8).split('|')
+      Seq.tabulate(outputSize) { i =>
+        val segments = lines(i + headerSize).split('|')
         QueryOutput(
           className = segments(1).trim,
           funcName = segments(2).trim,
@@ -177,7 +178,8 @@ class ExpressionsSchemaSuite extends QueryTest with SharedSparkSession {
     }
 
     // Compare results.
-    assert(expectedOutputs.size == outputs.size, s"Number of queries not equals")
+    assert(expectedOutputs.size == outputSize,
+      "The number of queries not equals the number of expected queries.")
 
     outputs.zip(expectedOutputs).foreach { case (output, expected) =>
       assert(expected.sql == output.sql, "SQL query did not match")