Improve tests (#1273)

Author: ccleva

core/src/test/java/tech/tablesaw/aggregate/AggregateFunctionsTest.java

@@ -323,7 +323,13 @@ void testMultipleColumnTypes() {
     StringColumn stringColumn = StringColumn.create("s", strings);
 
     Table table = Table.create("test", booleanColumn, numberColumn);
-    table.summarize(booleanColumn, numberColumn, countTrue, stdDev).by(stringColumn);
+    Table summary =
+        table.summarize(booleanColumn, numberColumn, countTrue, stdDev).by(stringColumn);
+
+    assertEquals(2.0, summary.doubleColumn(1).get(0), 1e-6);
+    assertEquals(0.0, summary.doubleColumn(1).get(1), 1e-6);
+    assertEquals(Math.sqrt(2), summary.doubleColumn(2).get(0), 1e-6);
+    assertEquals(Math.sqrt(2), summary.doubleColumn(2).get(1), 1e-6);
   }
 
   @Test

core/src/test/java/tech/tablesaw/joining/DataFrameJoinerTest.java

@@ -2006,7 +2006,7 @@ public void innerJoinEmptyLeftTable() {
   @Test
   public void leftOuterEmptyLeftTable() {
     Table leftTable = Table.create(StringColumn.create("Animal"));
-    Table joined = leftTable.joinOn("Animal").with(ANIMAL_NAMES).join();
+    Table joined = leftTable.joinOn("Animal").with(ANIMAL_NAMES).type(LEFT_OUTER).join();
     assertEquals(0, joined.rowCount());
     for (Column<?> column : joined.columnArray()) {
       assertEquals(0, column.size());

core/src/test/java/tech/tablesaw/util/DoubleArraysTest.java

@@ -14,6 +14,7 @@
 
 package tech.tablesaw.util;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import java.util.Arrays;
@@ -27,8 +28,9 @@ public class DoubleArraysTest {
   public void testTo2dArray() throws Exception {
     Table table = Table.read().csv("../data/tornadoes_1950-2014.csv");
     TableSliceGroup tableSliceGroup = table.splitOn("Scale");
-    int columnNuumber = table.columnIndex("Injuries");
-    DoubleArrays.to2dArray(tableSliceGroup, columnNuumber);
+    int columnNumber = table.columnIndex("Injuries");
+    double[][] a2dArray = DoubleArrays.to2dArray(tableSliceGroup, columnNumber);
+    assertEquals(7, a2dArray.length);
   }
 
   @Test