diff --git a/lang/unification/simplesolver_test.go b/lang/unification/simplesolver_test.go
new file mode 100644
index 00000000..cf46026f
--- /dev/null
+++ b/lang/unification/simplesolver_test.go
@@ -0,0 +1,190 @@
+// Mgmt
+// Copyright (C) 2013-2023+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build !root
+
+package unification
+
+import (
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/purpleidea/mgmt/lang/ast"
+	"github.com/purpleidea/mgmt/lang/interfaces"
+	"github.com/purpleidea/mgmt/lang/types"
+	"github.com/purpleidea/mgmt/util"
+)
+
+func TestSimpleSolver1(t *testing.T) {
+	type test struct { // an individual test
+		name       string
+		invariants []interfaces.Invariant
+		expected   []interfaces.Expr
+		fail       bool
+		expect     map[interfaces.Expr]*types.Type
+		experr     error  // expected error if fail == true (nil ignores it)
+		experrstr  string // expected error prefix
+	}
+	testCases := []test{}
+
+	{
+		expr := &ast.ExprStr{V: "hello"}
+
+		invariants := []interfaces.Invariant{
+			&interfaces.EqualsInvariant{
+				Expr: expr,
+				Type: types.NewType("str"),
+			},
+		}
+
+		invars, err := expr.Unify()
+		if err != nil {
+			panic("bad test")
+		}
+		invariants = append(invariants, invars...)
+
+		testCases = append(testCases, test{
+			name:       "simple str",
+			invariants: invariants,
+			expected: []interfaces.Expr{
+				expr,
+			},
+			fail: false,
+			expect: map[interfaces.Expr]*types.Type{
+				expr: types.TypeStr,
+			},
+		})
+	}
+	{
+		expr := &ast.ExprStr{V: "hello"}
+
+		invariants := []interfaces.Invariant{
+			&interfaces.EqualsInvariant{
+				Expr: expr,
+				Type: types.NewType("int"),
+			},
+		}
+
+		invars, err := expr.Unify()
+		if err != nil {
+			panic("bad test")
+		}
+		invariants = append(invariants, invars...)
+
+		testCases = append(testCases, test{
+			name:       "simple fail",
+			invariants: invariants,
+			expected: []interfaces.Expr{
+				expr,
+			},
+			fail: true,
+			//experr: ErrAmbiguous,
+		})
+	}
+
+	names := []string{}
+	for index, tc := range testCases { // run all the tests
+		if tc.name == "" {
+			t.Errorf("test #%d: not named", index)
+			continue
+		}
+		if util.StrInList(tc.name, names) {
+			t.Errorf("test #%d: duplicate sub test name of: %s", index, tc.name)
+			continue
+		}
+		names = append(names, tc.name)
+		t.Run(fmt.Sprintf("test #%d (%s)", index, tc.name), func(t *testing.T) {
+			invariants, expected, fail, expect, experr, experrstr := tc.invariants, tc.expected, tc.fail, tc.expect, tc.experr, tc.experrstr
+
+			logf := func(format string, v ...interface{}) {
+				t.Logf(fmt.Sprintf("test #%d", index)+": "+format, v...)
+			}
+			debug := testing.Verbose()
+
+			solver := SimpleInvariantSolverLogger(logf) // generates a solver with built-in logging
+
+			solution, err := solver(invariants, expected)
+			t.Logf("test #%d: solver completed with: %+v", index, err)
+
+			if !fail && err != nil {
+				t.Errorf("test #%d: FAIL", index)
+				t.Errorf("test #%d: solver failed with: %+v", index, err)
+				return
+			}
+			if fail && err == nil {
+				t.Errorf("test #%d: FAIL", index)
+				t.Errorf("test #%d: solver passed, expected fail", index)
+				return
+			}
+			if fail && experr != nil && err != experr { // test for specific error!
+				t.Errorf("test #%d: FAIL", index)
+				t.Errorf("test #%d: expected fail, got wrong error", index)
+				t.Errorf("test #%d: got error: %+v", index, err)
+				t.Errorf("test #%d: exp error: %+v", index, experr)
+				return
+			}
+
+			if fail && err != nil {
+				t.Logf("test #%d: err: %+v", index, err)
+			}
+			// test for specific error string!
+			if fail && experrstr != "" && !strings.HasPrefix(err.Error(), experrstr) {
+				t.Errorf("test #%d: FAIL", index)
+				t.Errorf("test #%d: expected fail, got wrong error", index)
+				t.Errorf("test #%d: got error: %s", index, err.Error())
+				t.Errorf("test #%d: exp error: %s", index, experrstr)
+				return
+			}
+
+			if expect == nil { // map[interfaces.Expr]*types.Type
+				return
+			}
+
+			solutions := solution.Solutions
+			if debug {
+				t.Logf("\n\ntest #%d: solutions: %+v\n", index, solutions)
+			}
+
+			solutionsMap := make(map[interfaces.Expr]*types.Type)
+			for _, invar := range solutions {
+				solutionsMap[invar.Expr] = invar.Type
+			}
+
+			var failed bool
+			// TODO: do this in sorted order
+			for expr, exptyp := range expect {
+				typ, exists := solutionsMap[expr]
+				if !exists {
+					t.Errorf("test #%d: solution missing for: %+v", index, expr)
+					failed = true
+					break
+				}
+				if err := exptyp.Cmp(typ); err != nil {
+					t.Errorf("test #%d: solutions type cmp failed with: %+v", index, err)
+					t.Logf("test #%d: got: %+v", index, exptyp)
+					t.Logf("test #%d: exp: %+v", index, typ)
+					failed = true
+					break
+				}
+			}
+			if failed {
+				return
+			}
+		})
+	}
+}