[MOREL-207] Detect and fix flaky tests

Revert the change of TypeMap.typeVars from HashMap to
LinkedHashMap; it is fine as a HashMap because it is never
iterated over.

Switch from assertEquals to assertThat.

Fixes #207

Co-authored-by: Julian Hyde <jhyde@apache.org>
Co-authored-by: Rette66 <wenxiuw2@illinois.edu>

src/main/java/net/hydromatic/morel/compile/CalciteCompiler.java

@@ -69,7 +69,7 @@
 
 import java.util.ArrayList;
 import java.util.Arrays;
-import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
@@ -775,7 +775,7 @@ private RelContext group(RelContext cx, Core.Group group) {
   }
 
   private static EvalEnv evalEnvOf(Environment env) {
-    final Map<String, Object> map = new HashMap<>();
+    final Map<String, Object> map = new LinkedHashMap<>();
     env.forEachValue(map::put);
     EMPTY_ENV.visit(map::putIfAbsent);
     return EvalEnvs.copyOf(map);

src/main/java/net/hydromatic/morel/compile/TypeMap.java

@@ -45,6 +45,13 @@ public class TypeMap {
   public final TypeSystem typeSystem;
   private final Map<AstNode, Unifier.Term> nodeTypeTerms;
   final Unifier.Substitution substitution;
+
+  /** Map from type variable name to type variable. The ordinal of the variable
+   * is the size of the map at the time it is registered.
+   *
+   * <p>This map is never iterated over, and therefore the deterministic
+   * iteration provided by LinkedHashMap is not necessary, and HashMap is
+   * sufficient. */
   private final Map<String, TypeVar> typeVars = new HashMap<>();
 
   TypeMap(TypeSystem typeSystem, Map<AstNode, Unifier.Term> nodeTypeTerms,

src/test/java/net/hydromatic/morel/MainTest.java

@@ -2114,7 +2114,7 @@ private static List<Object> node(Object... args) {
     final String ml = "from s in [\"abc\", \"\", \"d\"],\n"
         + "    c in explode s\n"
         + "  group s compute count = sum of 1";
-    ml(ml).assertEvalIter(equalsOrdered(list(3, "abc"), list(1, "d")));
+    ml(ml).assertEvalIter(equalsUnordered(list(3, "abc"), list(1, "d")));
   }
 
   @Test void testJoinLateral() {
@@ -2333,7 +2333,7 @@ private static List<Object> node(Object... args) {
         + "  group j = i mod 2\n"
         + "  compute sum of j")
         .assertType("{j:int, sum:int} list")
-        .assertEval(is(list(list(1, 5), list(0, 3))));
+        .assertEvalIter(equalsUnordered(list(1, 5), list(0, 3)));
 
     // "compute" must not be followed by other steps
     ml("from i in [1, 2, 3] compute s = sum of i yield s + 2")

src/test/java/net/hydromatic/morel/SatTest.java

@@ -22,6 +22,7 @@
 import net.hydromatic.morel.util.Sat.Term;
 import net.hydromatic.morel.util.Sat.Variable;
 
+import com.google.common.collect.ImmutableMap;
 import org.junit.jupiter.api.Test;
 
 import java.util.Map;
@@ -50,7 +51,8 @@ public class SatTest {
 
     final Map<Variable, Boolean> solution = sat.solve(formula);
     assertThat(solution, notNullValue());
-    assertThat(solution.toString(), is("{x=false, y=true}"));
+    assertThat(solution,
+        is(ImmutableMap.of(x, false, y, true)));
   }
 
   /** Tests true ("and" with zero arguments). */